WO2002086200A1

WO2002086200A1 - Production method for atomic and molecular patterns on surfaces and nanostructured devices

Info

Publication number: WO2002086200A1
Application number: PCT/IB2001/000668
Authority: WO
Inventors: Michael Brunner; Simon Berner; Thomas A. Jung; Hitoshi Suzuki
Original assignee: Universität Basel
Priority date: 2001-04-23
Filing date: 2001-04-23
Publication date: 2002-10-31

Abstract

A method for vapour-depositing atomic and/or molecular patterns (15) on a substrate (4) and nanoscale-devices produced by the method are disclosed. The method comprises the steps of choosing a substrate (4), at least two material components (3a; 25, 26) and their mixing ratio to form a specified self-organized atomic and/or molecular pattern (15) of the components (3a; 25, 26) by vapour-depositing them on the substrate (4). Embodiments refer e. g. to: intermingling the components (3a; 25, 26) on a truely atomic or molecular scale; forming periodic patterns (15); using an unstructured atomically planar or a pre-patterned deposition surface (4a); and building defects, dopants and/or functional molecules (18) into the specified pattern (15). The method is more flexible, simpler, more stable and less error-prone than conventional molecular pattern formation. Producible nanostructures (16a-16c, 22-23) comprise wires (16a) e. g. of C60-molecules (25), grids (16b), networks (16b), storage elements (22, 23) or diffraction gratings (16c).

Description

Production Method for Atomic and Molecular Patterns on Surfaces and Nanostructured Devices

TECHNICAL FIELD

The invention refers to the field of producing and struc- turing atomic or molecular patterns and devices on substrates .

BACKGROUND ART

In the article by J.V. Barth et al . , "Building Supramole- cular Nanostructures at Surfaces by Hydrogen Bonding" , Angew. Chem. Int. Ed. 2000, 39, No. 7, a method for producing chains of single-type organic molecules on metal surfaces is disclosed. The molecules are vapour-deposited under ultra-high vacuum by organic molecular beam epitaxy and form twin chains through self-assembly on the sub- strate. This method has several weaknesses. First of all, only twin chain patterns and no other types of regular patterns have been produced. The twin chain formation results from a fragile interaction between identical molecules and is rather unstable. Removing a single molecule can cause a deformation or even break-down of the whole twin chain. This makes integration of functional molecules difficult or impossible. The choice of the substrate material and symmetry uniquely determines the shape of the twin chain pattern. In particular, the twin chain cannot be manipulated or transformed into another ordered and stable pattern by varying process parameters or by other means. Only highly specific types of molecules may be useful for the twin chain formation. The method seems not to be adaptable to generate truely mono-molecular wires.

In the WO 98/35271 another method for creating a molecular pattern is disclosed. In a first step molecules of a certain type are uniformly vapour-deposited in ultrahigh vacuum on a copper crystal surface. In a second step a molecular pattern is created by using a scanning probe microscope (SPM) to select individual molecules and to switch them between bistable conformation states. For example, in one conformation the molecules may be moveable along the substrate surface by thermal excitation and diffusion, and in another conformation they may be fixed or pinned to the substrate surface. A third production step may include removal of molecules in one of the conformation states. The conformational molecular pattern can be useful in future display or storage technology. However, a pattern formation by individual addressing of molecules is time-consuming, susceptible to generating imperfections and requires a further development of presently available parallel SPM tip arrangements, such as millipede disclosed in the article by M. Lutwyche et al . , "Highly parallel data storage system based on scanning probe arrays", Applied Physics Letters Vol 77, No. 20, p.3299-3301 (2000). Furthermore, the practically achievable pattern complexity may be limited by the fact that the molecular pattern to be created must be traced molecule by molecule by the SPM tips.

In the U. S. Pat. No. 5,323,376 an atomic scale electro- nic switch is disclosed. The switch includes a plurality of closely separated electrodes. By applying voltages or currents a switching atom or molecule placed between the electrodes can be repositioned or reoriented such that an electrical contact between specified electrodes is esta- blished or interrupted. As well, a magnetic field or an atomic force microscopic tip or an optical beam may be used to change the conductivity of the switching atom or molecule between the electrodes.

In the article by H. Yanagi et al . , "Site-specific physi- sorption and chemical reaction of subphthalocyanine molecules on silicon(lll) - (7x7) " , Physical Review B, Vol.61, No.3, p.1959-1963, chloro [subphthalocyaninato]boron (III) or, in short, subphthalocyanine or SubPc molecules are disclosed. SubPc has an inner triazaporphyrin ring containing a Boron ion in the center and three peripheral benzene rings as side groups. The side groups have a di- stance between their centers of 0.76 nm and give rise to a three-fold rotational symmetry of the SubPc.

In an article by W. Kratschmer et al . , Nature, Vol.347, p.354, London (1990) or by W. Kroto et al . , Chem. Rev., Vol.91, p.1213-1235 (1991) the C₆o fullerene molecule is described. C₆o consists of 12 pentagons and 20 hexagons of carbon atoms and has a molecular weight of 720, a density of 1.72 g/cm², a molecular diameter of 0.7 nm and an in- finte rotational symmetry. All carbon atoms are equivalent and together form a delocalized π-system.

DISCLOSURE OF THE INVENTION

It is an object of the invention to provide a method for structuring atomic and/or molecular patterns on substrate surfaces, that are suitable for producing a larger variety of molecular patterns without resorting to a complica- ted, time-consuming and error-prone molecule-by-molecule processing. It is a further object to provide nanometer- scale devices that are producible by the said method. These objects are achieved by the subject-matter as set forth in the independent claims. Preferred embodiments are described in the dependent claims.

According to the independent method claim, a method for producing an atomic and/or molecular pattern on a substrate is disclosed, that comprises the steps of a) choosing a type of a substrate and preparing an atomi- cally clean deposition surface on the substrate, b) choosing a type and a mixing ratio of at least two material components for deposition on the substrate in order to generate a specified atomic and/or molecular pattern of the material components on the substrate, c) depositing under vacuum the material components from a gas phase onto the substrate, and d) forming or complementing the specified pattern by diffusion and self-organization of the material compo- nents on the substrate.

The deposition surface shall be atomically clean in the sense that impurity atoms or molecules unintentionally adhering to the deposition surface are only present in such negligible quanitities that induced defects in the pattern do not corrupt the functionality of the desired nanometer-scale devices. The substrate may be a metal, a semiconductor or an isolator and may have e. g. a glassy, quasiperiodic, periodic or otherwise regular structure. The chemical composition and mixing ratio of the material components are the key parameters to determine the shape and functionality of the atomic and/or molecular pattern to be formed on the deposition surface. The pattern exhibits regular features having a sub-micrometer and preferably sub-100 nm size. Typically the multi-component vacuum deposition requires for every material component a separate source of solid-state and/or liquid material. Solid source material is typically sublimated by heating. Liquid source material is evaporated, according to invention, through a leak valve into a small tube and then in- to the deposition chamber onto the substrate surface. During or after deposition the material components diffuse on the deposition surface and organize themselves into the specified pattern or nanostructure. As well, a pre- pattern may be present on the deposition surface, that is formed lithographically e. g. by electron beam, by molecule decoration with an SPM tip or by vapour-deposition and pinning of first components at predetermined sites on the deposition surface, e. g. by step decoration and growth starting at vicinally stepped surfaces. The pre- pattern is then complemented by diffusion and self- organization of further components vapour-deposited according to invention to form the specified pattern. The diffusion relies on spontaneous atomic or molecular movement by thermal excitation, but may be assisted by electric fields or other means. The self-organization takes place in such a way that the pattern reaches a favourable energetic and entropic state.

Advantages of the method are: high cleanliness and reliability and low error rate of the pattern formation process in vacuum, structural dimensions unobtainable by conventional lithographic processes, high integration density of up to terabyte/cm², pattern stability at room temperature, great variety of producible pattern geometries, great flexibility with respect to depositable materials and preparation of substrate surfaces, producibi- lity of atomically or molecularly regular patterns on large areas, suitability to automated mass-production, and compatibility with usual silicon production technology by using the same process steps in vacuum. A further advantage is the simple and economic producibility of nanometer-scale devices based on the proposed patterning method.

In a preferred embodiment the specified pattern shall be formed by intermingling atoms and/or molecules of the material components on an atomic or molecular scale. In other words, the type or chemical composition of the ma- terial components shall be chosen such that they form mixtures of their atoms and/or molecules on a nanometer scale at least for certain mixing ratios. For example, a minimum number of only two such non-segregating material components can be sufficient to produce, depending on the mixing ratio, a variety of pattern geometries useful for building nanoscale devices. The patterns may be specified for building nanometer-scale devices having electronic, magnetic, optical, nanomechanical, chemical, in particular biochemical, and/or biological functions. A further embodiment comprises the steps of forming at least in sections of the deposition surface a periodic or quasiperiodic pattern, which is preferably domain-free or single-domain, wherein the periodic pattern has unit cells that contain at least one atom or molecule of every deposited material component. Thus a two-dimensional monocrystal or polycrystal or mono- or poly-quasicrystal is formed. A periodic pattern is useful in many nanometer-scale devices, for example for providing arrays of massively parallel atomic or molecular wires or for providing periodic electronic or nuclear structures for x-ray or neutron diffraction gratings.

Another embodiment comprises steps of: selecting a monocrystalline substrate; preparing at least one atomi- cally planar region on the deposition surface; and/or depositing the material components epitaxially on the substrate. A monocrystalline substrate assures atomical periodicity of the deposition surface and can induce or favourably influence the pattern formation. It can further improve the adsorption stability at room temperature of the vapour-deposited atoms or molecules and hence of the pattern. An atomically planar region allows diffusion and self-oganization of the deposited material components undisturbed by geometric structures of the deposition surface. Epitaxial deposition is favourable in that a suitable substrate periodicity can be chosen and transferred to the pattern or can be used to modulate the pattern.

Other embodiments refer to modifying the shape and/or functionality of the deposited pattern by: modifying a chemical composition and/or a structure of the deposition surface, e. g. by using an SPM tip; building defects into the specified pattern during pattern formation through a suitably defect-inducing substrate material, deposition surface, and/or type and/or mixing ratio of the material components; and/or building dopants and/or functional mo- lecules preferably periodically into the specified pattern by depositing them before, during or after pattern formation. By means of chemical and/or structural substrate preparation, defect-inducing, doping and/or functional molecule insertion a great variety of patterns can be designed and adapted to support various technical functions useful in nanometer-scale devices.

Yet other embodiments refer to: regulating an amount of the material components for depositing a (sub-)monolayer forming a planar one- or two-dimensional nanostructure or for depositing a supra-monolayer forming a three-dimen- sional nanostructure; choosing the type and mixing ratio and regulating an amount of the material components for generating electrically conductive, semiconductive and/or insulating nanostructures, such as atomic and/or molecular wires, grids, networks, storage sites or diffraction gratings; preparing electrode terminals on the deposition surface for macroscopically contacting atomic and/or molecular nanostructures of the specified pattern; and/or repeating the steps of choosing a type and a mixing ratio of at least two material components and depositing them onto the substrate for successively generating superimposed patterns of the material components on the substrate. By controlling the pattern formation in one, two or three dimensions highly integrated nanometer-scale devices can be created. By repeated vapour deposition of pattern- forming material components versatile patterns or pattern stacks can be formed.

A more specific embodiment comprises the steps of choosing a monocrystalline silver substrate and as material components C_&0 fullerene molecules and SubPc molecules in order to generate wires of Cεσ molecules on the substrate. In particular, a distance between parallel neighbouring Cβo-wires can be varied by modifying side groups of the SubPc molecules. Furthermore, a two-dimensional lattice or raster of SubPc molecules providing empty sites filla- ble with Ceo fullerene molecules can be built. According to the independent device claim, a nanometer- scale device, in particular produced according to the method described above, comprises a substrate with an ato- mically clean deposition surface and at least two materi- al components deposited in vacuum from a gas phase on the substrate, wherein a type of the substrate and a type and mixing ratio of the material components are present such that the material components are arranged in a predetermined self-organized atomic and/or molecular pattern. Preferred nanometer-scale devices are producible according to preferred embodiments of the pattern formation method.

In one embodiment the pattern comprises at least one sub- monolayer, monolayer or supra-monolayer of the material components organized in electrically conductive, semi- conductive or insulating nanostructures, such as atomic and/or molecular wires, grids, networks, storage sites or diffraction gratings. In particular, the nanometer-scale device comprises electrode terminals for contacting the nanostructures and/or the nanometer-scale device is equipped with operating means, such as scanning probe microscope tips, for addressing and/or manipulating atoms and/or molecules of the nanostructures.

In another embodiment the nanostructures of the pattern comprise molecules having a large dielectric polarizabi- lity and/or a delocalized electron system and/or a specified rotational symmetry. In particular, the nanostructures comprise parallel wires of Cεo fullerene molecules spaced apart by interstitial SubPc molecules. More specific embodiments comprise: an atomic or molecular wire connecting two spaced apart electrode terminals; an atomic or molecular wire having a reversibly removable and insertable or a bistably switchable atom or molecule for opening and closing the wire and thereby performing a switching operation; an atomic or molecular wire branching into at least two atomic or molecular wires, wherein an atom or molecule is reversibly movable between branched wires for performing a relaying operation; a two-dimensional pattern of atoms, molecules and/or defects, wherein at least one type of atom, molecule or de- feet is reversibly removable from and insertable into or repositionable within the pattern for storing information; and/or an array of parallel equidistant atomic or molecular wires for X-ray diffraction. Nanometer-scale devices for electrical applications, that in particular comprise conductive or semiconductive atomic or molecular structures or elements, are preferably formed on an electrically insulating deposition surface, e. g. by using an insulating substrate or by coating an arbitrary substrate with an insulating layer. In a further embodiment the nanometer-scale device comprises an electrically addressable atomic and/or molecular matrix comprising a grid of conductive atomic or molecular wires and electronically switchable atoms or molecules located at crossing points of the wires and means for selectively applying voltages or currents to pairs of crossing wires for switching the switchable atoms or molecules between different conductivity states for information storage or other purposes. The different conductivity states may be related e. g. to different orienta- tion, conformation or electron configuration states of the switchable atoms or molecules.

Other objects and advantages of the present invention and other embodiments will become apparent from the description in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is exemplified by the drawings showing in Fig. 1 an ultra high vacuum chamber for vapour deposition of molecular patterns according to invention;

Fig. 2-5 atomic or molecular wires producible by vapour deposition and eventually comprising functional molecules ;

Fig. 6 a mechanically addressable atomic or molecular storage element producible by vapour deposition;

Fig. 7a and Fig. 7b an electrically addressable atomic or molecular storage, display or information processing element producible by vapour deposition;

Fig. 8 an atomic or molecular diffraction grating producible by vapour deposition; and

Fig. 9-10 model molecular patterns produced by vapour de- position of Ceo and subphtalocyanine molecules.

In the drawings identical parts are designated by identical reference numerals.

MODES FOR CARRYING OUT THE INVENTION

Fig. 1 shows an exemplary molecular vapour deposition chamber 1 for producing atomic and/or molecular patterns 15. The chamber 1 comprises an evaporation stage 2 carrying several evaporators 3 filled with solid-state or liquid material components 3a to be deposited on the sample or substrate 4. In the case of liquid source mate- rial 3a the evaporator 3 comprises a leak valve and a tube or nozzle for spraying the material component 3a into the deposition chamber 1. The evaporation stage 2 is mounted on a rod 5 that has a turning knob 6 and vertical positioning means 7, such as bellows and a screw, for adapting the orientation and height of the evaporation stage 2 in the chamber 1. The sample 4 is mounted on a sample stage 8 held by a manipulator 9 for transporting it between a storage chamber la (indicated on the right), the deposition chamber 1, a preparation chamber lb (indicated on the left) , possibly further chambers (not shown) , such as a scanning probe microscope (SPM) chamber for substrate pre-patterning or deposition-pattern postprocessing, and a fast entry air look (not shown) . The manipulator 9 also serves for translating and rotating the substrate 4 with its properly prepared deposition surface 4a into a suitable position and orientation within the chamber 1 for molecular vapour deposition. The sample stage 8 can be equipped with a heating/cooling element for temperature adjustment of the substrate 4, in particular for substrate annealing. For practical purposes a fork 10 for intake of atomic or molecular evapora- tion material 3a and delivery to the evaporators 3 is integrated in the sample stage 8.

The evaporation rate is measured by a micro-balance 11 equipped with a quartz oscillator 12. The micro-balance 11 is water-cooled and has an extremely high precision to control sub-monolayer depositions. It is also adaptable in height by positioning means 13. The deposition chamber 1 is isolated from neighbouring chambers la, lb by gate valves 14. The deposition chamber 1 is evacuated by ultra high vacuum pumps (not shown) , such as an ion pump, a ti- tanium sublimation pump and/or a turbo pump, that are well known by the skilled person.

The apparatus 1 is designed for performing the method according to invention of producing atomic and/or molecular nanometer-structures 16a-16c, 22-23. First, the substrate 4 and at least two material components 3a are chosen. The substrate 4 is mounted on the sample stage 8, an atomi- cally clean deposition surface 4a is prepared on the substrate 4 e. g. in the preparation chamber lb, the material components 3a are filled into the evaporators 3 with the fork 10, and the stage 8 is translated into the storage chamber la. Then the evaporators 3 are heated one at a time or in combination and the evaporation rates are set to a desired level. The substrate 4 is transported into the deposition chamber 1 and its deposition surface 4a is exhibited to the evaporated molecules 3a for a cer- tain time for depositing a predetermined amount and mixing ratio of the material components 3a. Depending on the type of the substrate 4 and the material components 3a and on the relative and absolute deposition quantities of the material components 3a the specified atomic and/or molecular pattern 15 is formed by diffusion and self- organization of the deposited atoms and/or molecules 3a on the deposition surface 4a. The spontaneous pattern formation is a much simpler and much more flexible process than conventional methods using mechanical pat- tern formation by SPM tips or substrate-induced pattern formation, such as molecular decoration of atomic steps. Some preferable embodiments of the pattern forming method are described below.

The diffusion and self-organization may be induced, assi- sted or accelerated by annealing the substrate 4 during or after deposition of the material components 3a. A buried nanostructure layer may be formed by depositing a fixation and protection layer onto the pattern 15 on the substrate 4 for electrical, chemical and mechanical pro- tection.

The pattern formation can comprise the steps of selecting and/or modifying nanostructures 16a-16c, 22-23 of atoms and/or molecules of the material components 3a within the specified pattern 15 for building nanometer-scale devi- ces. The nanostructures 16a-16c, 22-23 may be formed with a precision better than 50 nm, in particular 20nm, and preferably with a molecular or atomic precision.

A pre-pattern can be formed on the deposition surface 4a, which pre-pattern comprises atomic and/or molecular geo- metric configurations, such as atomic and/or molecular islands, indentations or steps. The pre-pattern is a tool for modifying the self-organized vapour deposited pattern 15 and/or for introducing additional features into the self-organized pattern 15 that are useful in the design of nanometer-scale devices. Similarly, defects, dopants and/or functional molecules 18 can be incorporated into the specified deposited pattern 15, for example by modifying the substrate material 4, the deposition surface 4a, the type and/or mixing ratio of the material components 3a, or by an additional deposition process before, on or after pattern formation. The skilled person can combine the present invention with any modification of the deposition surface 4a and with insertion of any type of defect, dopant, functional element 18 and/or atomic or molecular function in general, as known in the state of the art and as being, in particular, mentioned in the U. S. Pat. No. 4,987,312, U. S. Pat. No. 5,323,376, EP 0 548 905, WO 98/35271, U. S. Pat. No. 5,453,970, and WO 99/15895 the disclosures of which are herewith incorporated into the specification in their entirety by refe- rence.

Additional production steps may be: characterizing the pattern 15 by diffraction methods, such as low energy electron diffraction (LEED) , reflection high energy electron diffraction (RHEED) , extended x-ray absorption fine structure (EXAFS) , or x-ray photo-electron diffraction (XPD) , or by spatially resolving methods, such as scanning electron microscopy (SEM) or scanning probe microscopy (SPM) , such as scanning tunneling microscopy (STM) , atomic force microscopy (AFM) or scanning near-field op- tical microscopy (SNOM) ; and/or further processing of the pattern 15 by manipulating atoms and/or molecules on the substrate 4 with a scanning probe microscope (SPM) , such as an STM or an AFM, e. g. by inserting between atomic and/or molecular wires 16a electrically conductive atoms or molecules 18 or bistable or multistable molecular switches 18 or by storing atoms, molecules or defects 18 in molecular storage sites 23. In a second aspect the invention pertains to any nanometer-scale device produced according to the method described above. Such a device comprises a substrate 4 with an atomically clean deposition surface 4a and with at least two material components 3a deposited in vacuum from a gas phase on the substrate 4, wherein a type of the substrate 4 and a type and mixing ratio of the material components 3a are present such that the material components 3a are arranged in a predetermined atomic and/or molecular pattern 15 that has been formed by diffusion and self- organization of the material components 3a on the substrate 4. Preferred embodiments are described below.

The pattern 15 can comprise atoms and/or molecules of the material components 3a that are mixed together on an ato- mic or molecular scale. In particular, the pattern 15 comprises periodic and preferably domain-free or single- domain sections with unit cells that contain at least one atom or molecule of every deposited material component 3a. The mixing of different atoms and molecules 3a gua- rantees that patterns 15 or nanostructures 16a-16c, 22-23 are formed with truly nanometer-sized dimensions and, in particular, with atomic or molecular precision. Furthermore, wires of mono-molecular width can be stably formed due to the intermolecular interactions between the at least two vapour-deposited species and due to the molecule-substrate interactions. The vapour deposition of several pattern-forming components or species instead of a single one gives unique advantages: A larger variety of atoms or molecules may be useful, a plurality of diffe- rent patterns can be formed and different patterns can be created with the same species by simply varying their mixing ratio and absolute amounts. The multi-component patterns have an improved stability and can be post- processed, in particular equipped with functional molecu- les, without being disturbed. The nanometer-scale device is producible on an atomically planar region of the deposition surface 4a, quite in contrast to previous methods such as molecule decoration on atomic steps of the deposition surface 4a. The nanometer- scale device shall be designed to perform electronic, magnetic, optical, nanomechanical , chemical, biochemical and/or biological operations, such as information storage and processing, beam diffraction, and/or sensing applications. For this purpose, pattern features induced by the deposition surface 4a, defects, dopants and/or functional molecules or elements 18 can be incorporated into the pattern 15 or nanometer-scale device. For certain applications, such as atomic or molecular integrated circuits or electronics (Fig. 2-5) , it is preferred to provide an electrically insulating substrate 4a, e. g. NaCl, CaF₂, or MgO.

Fig. 2-5 show schematic exemplary embodiments of the atomic and/or molecular patterns 15 or nanostructures 16a- 16c, 22-23 that are producible by the disclosed multi- component vapour deposition method. Fig. 2 shows a conductive or semiconductive atomic or molecular wire 16a connecting two electrode pads or terminals 17, that can be produced by conventional lithography and can be contacted by usual macroscopic wiring techniques. Note that the wire 16a is formed by at least one vapour-deposited atomic or molecular species 3a (round symbols) and is typically surrounded by another vapour-deposited atomic or molecular species 3a (triangular symbols).

Fig. 3 shows an atomic or molecular wire 16a equipped with a position switch 18. The position switch 18 is embodied by a functional atom or molecule 18, that is reversibly removable to interrupt the wire 16a or inserta- ble to close the wire 16a electrically. The switching atom or molecule 18 can for example be moved by a SPM tip (not shown) . Similarly, Fig. 4 shows an atomic or molecular wire 16a equipped with a conformational switch 18 that is embodied by a bistable atom or molecule 18. The bistable element 18 is switchable between a first state with small conductivity (right hand side) to interrupt the wire 16a and a second state with large conductivity (left hand side) to close the wire 16a. As well, the bistable states can differ by molecular conformation, spatial distribution of electron orbitals, or by any other difference in their electronic, optical or mechanical structure. Reversible switching can be effected by the SPM tip 19 generating a local (e. g. mechanical, electrical, magnetical or optical) switching field 20, as is shown in the WO 98/35271.

Fig. 5 shows a branched atomic or molecular wire 16a equipped with a relaying atom or molecule 18. The relay 18 is switchable between two or more branches of the wire 16a and renders either of the branches 16a conductive and the other branch or branches 16a disconnected by leaving an empty position 21.

Fig. 6 shows an atomic or molecular storage medium 15 comprising a frame, lattice or periodic raster of stable molecules 22 and vacancies or storage sites 23, that can be occupied with a molecule species 18 or can be empty. Note that the stable lattice atoms or molecules 22 can be one or several species and that storage atoms or molecu- les 18 can be different from or identical with the lattice atoms or molecules 22. Placement and replacement of the storage atoms or molecules 18 can again be effected by a SPM tip 19, as disclosed e. g. in the U. S. Pat. No. 4,987,312. The storage density of the nano-storage device or storage element 22, 23 reaches terabyte/cm².

Fig. 7a shows an electrically addressable atomic and/or molecular matrix 16b comprising a grid of conductive atomic or molecular wires 16a and electronically switchable bistable atoms or molecules 18 located at crossing points of the wires 16a. The nanometer-scale device further comprises means (not shown) for selectively applying volta- ges and/or currents to pairs of crossing wires 16a for switching the switchable atoms or molecules 18 between different conductivity states (fat open symbols 18 or full symbols 18) for information storage, display appli- cations or other purposes. The different conductivity states of the switchable atoms or molecules 18 may be related to different orientation, conformation or electron configuration states.

Fig. 7b shows a modified matrix or network 16b wherein first parallel atomic or molecular wires 16a are vertically separated by an inter-layer 24 from perpendicularly oriented second parallel wires 16a. Switching molecules 18 may be present at crossing points of the first and second wires 16a and may be comprised in either the first plane, the inter-layer 24 or the second plane. In general the first and second wires 16a may be angularly shifted by arbitrary rotation angles, e. g. by 45°, 60° or 90° (as shown) . The inter-layer 24 may be a semiconducting or isolating layer 24 with a thickness of e. g. 1-10 mono- layers that may be tunnelled through at crossing points of the wires 16a to switch the functional molecules or switches 18. Similarly, in Fig. 4 the functional molecule 18 can be separated from the wire 16a by an inter-layer 24 (not shown) . In the Fig. 2-7b the functional atoms or molecules 18 may be inserted into the pattern 15 or nanostructures 16a- 16c, 22-23 by any means, for example by mechanical placement with a SPM tip 19, by any deposition technique (e. g. also by the disclosed vapour deposition tech- nique) , or by substrate pre-patterning. Doping of nanostructures 16a-16c, 22-23 may be useful for producing semiconducting elements such as semiconducting wires 16a, diodes, light emitting diodes (LED) , laser diodes (LD) , transistors, quantum computing devices etc. In particu- lar, an atomic or molecular diode, LED or LD may be pro- duced at crossing points of n-doped and p-doped semiconductive atomic or molecular wires 16a.

Fig. 8 shows an example of a parallel arrangement of atomic and/or molecular wires 16a that can be used for x-ray or neutron diffraction. Thereby, an incoming beam 27 is diffracted into an outgoing beam 28 by certain angles Φ. It is of great advantage that the atomic or molecular diffraction grating 16c can be produced efficiently and still with atomic or molecular alignment precision. Furthermore, a distance between parallel neighbouring wires 16a, e. g. made from C₆o molecules 25, can be modified by varying side groups of interstitially arranged spacer molecules, e. g. SubPc molecules 26. With respect to SubPc, the disclosure of H. Yanagi, Physical Review B, Vol.61, No.3, p.1959-1963 is herewith incorporated in its entirety into the specification by reference. Modified side groups may comprise naphthalene or anthrazene rings. Other molecular design parameters are the molecular dimensions and the rotational symmetry, also in relation to the lattice constant and symmetry of the substrate 4. Note that the SubPc with 3-fold rotational symmetry may be replaced by a porphyrin molecule with a 4-fold rotational symmetry, as disclosed in the WO 98/35271, or by a de- cacyclene molecule with a 6-fold rotational symmetry, as disclosed in the article by J. K. Gimzewski et al . , "Rotation of a Single Molecule Within a Supramolecular Bearing" , Science, Vol.281, p.531-533 (1998), the disclosure of which is herewith incorporated into the specification in its entirety by reference. Fig. 9 and 10 show experimentally formed model patterns 15 formed by vapour depositing C₆o and SubPc molecules 25, 26 in various mixing ratios on a monocrystalline silver Ag(lll) substrate 4. The vapour deposition is performed at room temperature at a deposition rate of typically 1 monolayer per minute. In Fig. 9 a certain mixing ratio has been chosen to form parallel essentially linear wires 16a of C₆o molecules 25 laterally spaced apart by hexago- nally aranged SubPc molecules 26. In Fig. 10 the mixing ratio has been changed to achieve a decreased Ceo density on the deposition durface 4a. As a consequence the model pattern 15 comprises a regular raster or lattice of stable molecules 22, namely SubPc molecules 26, that are arranged hexagonally and provide storage sites 23 in their centres. The storage sites 23 can be empty (left hand side) or filled with C₆o molecules 25 (right hand side) . As well, stably adsorbed C_δo molecules 25 are present. Thus the model pattern 15 is useable as a storage medium 22, 23.

While there are shown and described presently preferred embodiments of the invention, it is to be distinctly un- derstood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.

Claims

1. A method for producing an atomic and/or molecular pattern (15) on a substrate (4), comprising the steps of a) choosing a type of a substrate (4) and preparing an atomically clean deposition surface (4a) on the substrate (4) , b) choosing a type and a mixing ratio of at least two material components (3a) for deposition on the substrate (4) in order to generate a specified atomic and/or molecular pattern (15) of the material components (3a) on the substrate (4) , c) depositing under vacuum the material components (3a) from a gas phase onto the substrate (4) , and d) forming or complementing the specified pattern (15) by diffusion and self-organization of the material components (3a) on the substrate (4) .

2. The method according to claim 1, comprising the steps of a) forming the specified pattern (15) by intermingling atoms and/or molecules of the material components (3a) on an atomic or molecular scale and/or b) using the specified pattern (15) for building nanometer-scale devices, in particular for elec- tronic, magnetic, optical, nanomechanical, chemical and/or biological applications.

3. The method according to one of the previous claims, comprising the steps of a) selecting and/or modifying nanostructures (16a- 16c, 22-23) of atoms and/or molecules of the material components (3a) within the specified pattern (15) for building nanometer-scale devices and/or b) forming the nanostructures (16a-16c, 22-23) with a precision of better than 50 nm, in particular 20nm, and preferably with a molecular or atomic precision.

4. The method according to one of the previous claims, comprising the steps of a) forming at least in sections of the deposition surface (4a) a periodic or quasiperiodic pattern (15), which is preferably domain-free or single- domain, b) wherein the periodic pattern (15) has unit cells that contain at least one atom or molecule of every deposited material component (3a) .

5. The method according to one of the previous claims, comprising the steps of a) using a monocrystalline substrate (4) and/or b) preparing at least one atomically planar region on the deposition surface (4a) and/or c) depositing the material components (3a) epitaxial- ly on the substrate (4) and/or d) preparing an electrically insulating deposition surface (4a) .

6. The method according to one of the previous claims, comprising the steps of a) modifying a chemical composition and/or a structure of the deposition surface (4a) in order to generate a modified pattern (15) of the material components (3a) on the substrate (4) and b) in particular, preparing a pre-pattern comprising atomic and/or molecular geometric configurations, such as atomic and/or molecular islands, indentations or steps, on the deposition surface (4a) .

7. The method according to one of the previous claims, comprising the steps of a) building defects into the specified pattern (15) during pattern formation by providing a suitably defect-inducing substrate material (4) , deposition surface (4a) , and/or type and/or mixing ratio of the material components (3a) and/or b) building dopants and/or functional molecules (18) into the specified pattern (15) by depositing them before, during or after pattern formation, c) in particular, building defects, dopants and/or functional molecules (18) periodically into the specified pattern (15) .

8. The method according to one of the previous claims, comprising the step of a) regulating an amount of the material components (3a) for depositing a sub-monolayer or a monolayer in order to generate a pattern (15) comprising a planar one- or two-dimensional nanostructure (16a- 16c, 22-23) or b) regulating an amount of the material components (3a) for depositing a supra-monolayer in order to generate a pattern (15) comprising a three- dimensional nanostructure (16a-16c, 22-23) .

9. The method according to one of the previous claims, comprising the steps of a) choosing the type and mixing ratio and regulating an amount of the material components (3a) for generating electrically conductive, semiconductive and/or insulating nanostructures (16a-16c, 22-23), such as atomic and/or molecular wires (16a), grids (16b), networks (16b), storage elements (22, 23) or diffraction gratings (16c), and/or b) preparing electrode terminals (17) on the deposition surface (4a) for contacting atomic and/or molecular nanostructures (16a, 16b) of the specified pattern (15) and/or c) repeating the steps of choosing a type and a mixing ratio of at least two material components (3a) and depositing them onto the substrate (4) in order to successively generate superimposed patterns (15) of the material components (3a) on the substrate (4) .

10. The method according to one of the previous claims, comprising the steps of a) using an ultra-high vacuum for deposition and pattern formation of the material components (3a) and/or b) depositing the material components (3a) simultaneously or one after the other onto the substrate (4) and/or c) annealing the substrate (4) during or after depo- sition of the material components (3a) and/or d) depositing a fixation and protection layer onto the pattern (15) on the substrate (4) .

11. The method according to one of the previous claims, comprising the steps of a) choosing as a material component (3a) molecules

(3a; 25, 26) with a large dielectric polarizabili- ty, and b) in particular, choosing molecules (3a; 25, 26) comprising a delocalized electron system, such as fullerenes (25) .

12. The method according to claim 11, comprising the steps of a) choosing a monocrystalline silver substrate (4) and as material components (3a) Ceo fullerene mole- cules (25) and SubPc molecules (26) in order to generate wires (16a) of Ceo molecules (25) or a raster of SubPc molecules (26) on the substrate (4) and b) in particular, varying a distance between parallel neighbouring C_δo-wires (16a) by modifying side groups of the SubPc molecule (26) .

13. The method according to one of the previous claims, comprising the steps of a) characterizing the pattern (15) by diffraction me- thods, such as low energy electron diffraction

(LEED) , reflection high energy electron diffraction (RHEED) , extended x-ray absorption fine structure (EXAFS) , or x-ray photo-electron diffraction (XPD) , or by spatially resolving methods, such as scanning electron microscopy (ΞEM) or scanning probe microscopy (SPM; STM, AFM, SNOM) and/or b) further processing of the pattern (15) by manipulating atoms and/or molecules on the substrate (4) with a scanning probe microscope (SPM; STM, AFM) , e. g. by inserting between atomic and/or molecular wires (16a) electrically conductive atoms or molecules (18) or bistable or multistable molecular switches (18) or by storing atoms, molecules or defects (18) in molecular storage sites (23) .

14. A nanometer-scale device, in particular produced ac- cording to the method according to one of the previous claims, comprising a substrate (4) with an atomically clean deposition surface (4a) and at least two material components (3a) deposited in vacuum from a gas phase on the substrate (4) , wherein a type of the substrate (4) and a type and mixing ratio of the material components (3a) are present such that the material components (3a) are arranged in a predetermined self-organized atomic and/or molecular pattern (15) .

15. The nanometer-scale device according to claim 14, wherein a) the pattern (15) comprises atoms and/or molecules of the material components (3a) mixed together on an atomic or molecular scale and b) in particular, the pattern (15) comprises periodic and preferably domain-free or single-domain sections with unit cells that contain at least one atom or molecule of every deposited material component (3a) .

16. The nanometer-scale device according to one of the claims 14-15, wherein a) the nanometer-scale device is formed on an atomically planar region of the deposition surface (4a) and/or b) the nanometer-scale device comprises pattern features induced by the deposition surface (4a) and/or c) the nanometer-scale device comprises built-in de- fects, dopants and/or functional molecules (18) .

17. The nanometer-scale device according to one of the claims 14-16, wherein the nanometer-scale device is designed to perform electronic, magnetic, optical, nanomechanical, chemical and/or biological opera- tions, such as information storage and processing, beam diffraction, and/or sensing applications.

18. The nanometer-scale device according to one of the claims 14-17, wherein a) the pattern (15) comprises at least one sub- monolayer, monolayer or supra-monolayer of the material components (3a) organized in electrically conductive, semiconductive or insulating nanostructures (16a-16c, 22-23) , such as atomic and/or molecular wires (16a) , grids (16b) , networks (16b), storage elements (22, 23) or diffraction gratings (16c) , and b) in particular, the nanometer-scale device comprises electrode terminals (17) for contacting the nanostructures (16a, 16b) and/or the nanometer- scale device is equipped with operating means, such as scanning probe microscope tips (19), for addressing and/or manipulating atoms and/or molecules (18) of the nanostructures (16a, 16b; 22- 23) .

19. The nanometer-scale device according to one of the claims 14-18, wherein a) nanostructures (16a-16c, 22-23) of the pattern

(15) comprise molecules (3a; 25, 26) having a large dielectric polarizability and/or a deloca- lized electron system and/or a specified rotational symmetry and b) in particular, the nanostructures (16a, 16b, 16c) comprise parallel wires (16a) of C₆o fullerene mo- lecules (25) spaced apart by interstitial SubPc molecules (26) .

20. The nanometer-scale device according to one of the claims 14-19, comprising a) an atomic or molecular wire (16a) connecting two spaced apart electrode terminals (17) and/or b) an atomic or molecular wire (16a) having a reversibly removable and insertable or a bistably switchable atom or molecule (18) for opening and closing the wire (16a) and thereby performing a swit- ching operation and/or c) an atomic or molecular wire (16a) branching into at least two atomic or molecular wires (16a), wherein an atom or molecule (18) is reversibly movable between branched wires (16a) for performing a relaying operation and/or d) a two-dimensional pattern (15) of atoms, molecules and/or defects (22, 18), wherein at least one type of atom, molecule or defect (18) is reversibly removable from and insertable into or repositionable within the pattern (15) for storing information and/or e) an array of parallel equidistant atomic or molecular wires (16a) for x-ray diffraction.

21. The nanometer-scale device according to one of the claims 14-20, comprising a) an electrically addressable atomic and/or molecular matrix (16b) comprising a grid of conductive atomic or molecular wires (16a) and electronically switchable atoms or molecules (18) located at crossing points of the wires (16a) and b) means for selectively applying voltages and/or currents to pairs of crossing wires (16a) for switching the switchable atoms or molecules (18) between different conductivity states for information storage or other purposes, c) wherein, in particular, the different conductivity states are related to different orientation, con- formation or electron configuration states of the switchable atoms or molecules (18) .