RU2519094C1 - Method of exfoliation of layered crystalline materials - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method includes exfoliation of blanks from layered crystalline materials, fixed on one side on gliphtale support, with application of adhesive tape, when exfoliation is completed, gliphtale is dissolved in acetone, where suspension of crystalline plates (layers) of metal chalcogenides is formed, the latter are separated from suspension by their precipitation on substrate.

EFFECT: invention makes it possible to obtain layers of nanosized thickness from layered crystals with possibility of further precipitation on different substrates.

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Description

The development of nanotechnology stimulates the growth of scientific interest in layers and films of crystalline materials having nanoscale thickness. From the moment graphene was obtained by mechanical peeling of graphite layers [K.S. Novoselov,

A.K. Geim, S.V. Morozov et al. Electric field effect in Atomically thin carbon films. Science, 2004, v. 306, p.666], intensive development of methods for exfoliating layered materials structurally similar to graphite is underway, as well as searches for methods of transferring layers of nanoscale thickness to various substrates to study properties and to ensure practical applications of such layers. This primarily relates to metal chalcogenide crystals having a hexagonal structure with weak bonds between the layers in the direction of the <0001> axis (GaS, GaSe, GaTe, Bi2Se3, BiTe3).

Known methods of laser and thermal exfoliation of GaSe and GaS [U.K. Gautam

S. R. C. Vivekchand, A. Govindaraj et al. Generation of onions and nanotubes of GaS and GaSe through laser and thermally induced exfoliation. J. Am. Chem. Soc., 2005, v. 127, 3658-3659] - analogue. Laser exfoliation occurs when a suspension of GaSe or GaS powder in an organic liquid, such as toluene, is processed by laser radiation with a wavelength of 532 nm. Thermal exfoliation is performed by heating the powders to 900 ° C in a closed volume. However, these methods are designed to produce nanotubes and the so-called. “Onion” nanostructures and technically do not allow the preparation of layers of nanoscale thickness with their subsequent transfer to the substrate.

A known method of mechanical exfoliation of a graphite billet, mounted on one side on a support of optical fiber, to obtain graphene on the surface of the optical fiber [S.Y. Won. Method for manufacturing pulsed laser using graphene prepared by mechanical exfoliation. Application number KR 20100090781 20100915, 2012] is a prototype. The method consists in the fact that the graphite preform is fixed on one side to the optical fiber by pressing the optical fiber into graphite, and then the graphite is mechanically exfoliated from the opposite side of the graphite preform using adhesive tape. So you can get graphene layers directly on the surface of the optical fiber, but the method does not allow you to transfer them to other substrates.

The objective of the invention is to obtain layers of nanoscale thickness from layered crystals with the possibility of subsequent deposition of layers on various substrates.

The problem is solved by mechanical exfoliation of blanks from layered crystals, fixed on one side to a support, using adhesive tape. In this case, the preform is fixed on a support made of gliptal, and at the end of exfoliation, the gliptal dissolves in acetone with the formation of a suspension of crystalline layers of nanoscale thickness, after which the layers are separated from the suspension by depositing them on the desired substrate.

For the convenience of the process, the gliptal can be applied in a thin layer on an arbitrary base, for example, on polished quartz glass.

The proposed method of exfoliation allows you to obtain layers of nanoscale thickness and transfer the resulting layers to any desired substrate.

Example 1

A GaSe single crystal is mechanically split along the cleavage plane (0001). Then, the crystal is again chipped parallel to the already obtained chip so that a preform with a thickness of about 0.1 mm is formed. The workpiece is tightly pressed to the gliptal at a temperature of 60 ° C, then it is cooled together with the gliptal to room temperature, after which exfoliation is performed on the second side of the workpiece using adhesive tape ("adhesive tape") on a polymer basis. The removal of GaSe with adhesive tape is carried out until gallium selenide continues to exfoliate. At the end of this process, thin, predominantly nanosized thickness, GaSe films remain on the gliptal, which no longer mechanically peel off using tape. Glyptal is dissolved in acetone, which leads to the formation of a suspension of crystalline layers of nanoscale thickness, because layers of greater thickness quickly settle to the bottom. The layers are separated from the suspension by depositing them on single crystal silicon substrates. GaSe layers of nanosized thickness (about 10 nm) on silicon substrates were obtained. Such a layer is shown in FIG. 1, where an optical micrograph (635 μm horizontal and 458 μm vertical) of a GaSe layer about 10 nm thick on a single-crystal silicon substrate is shown. In the photograph of FIG. 1, the GaSe-free surface of the substrate looks like a dark background.

Example 2

A GaS single crystal is mechanically split along the cleavage plane (0001). Then, the crystal is again chipped parallel to the already obtained chip so that a preform of a thickness of about 0.2 mm is formed. The workpiece is tightly pressed to the gliptal at a temperature of 50 ° C, then it is cooled together with the gliptal to room temperature, after which exfoliation is carried out on the second side of the workpiece using adhesive tape ("adhesive tape") on a polymer basis. Removing GaS with an adhesive tape is carried out until gallium sulfide continues to exfoliate, then gliptal, on the surface of which thin, mainly nanosized thickness layers of gallium sulfide remain, are dissolved in acetone, which leads to the formation of a suspension of crystalline layers of nanosized thickness. The layers are separated from the suspension by depositing them on substrates of single crystal silicon, passivated by oxidation. GaS layers of nanosized thickness (about 15 nm) on oxidized silicon substrates were obtained. Such a layer is shown in FIG. 2, where an optical micrograph (635 μm horizontal and 458 μm vertical) of a GaS layer about 15 nm thick on an oxidized single-crystal silicon substrate is presented. On top of the GaS plate (pos. 1 in Fig. 2), gold contacts are deposited nanolithographically (pos. 2 in Fig. 2, one of the 24 contacts is marked), which makes it possible to measure the electrical characteristics of the GaS nanolayer. Figure 3 presents the results of measuring the thickness of the GaS layer near the applied contact using atomic force microscopy (the abscissa shows the distance in microns traveled by the microscope probe, the ordinate shows the height in nm relative to the substrate plane). The thickness of the GaS layer without contact is about 15 nm, the thickness of the gallium sulfide layer with the contact is about 24-25 nm.

Claims (1)

A method of exfoliating layered crystalline materials using adhesive tape, comprising exfoliating preforms of layered crystalline materials fixed on one side to a support, characterized in that the support is a gliptal that is dissolved in acetone upon completion of exfoliation, where a suspension of nanosized crystal plates forms metal chalcogenides then deposited on a substrate.

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