JPH04116163A - Production of silver single crystal thin film and artificial metal lattice - Google Patents

Abstract

PURPOSE:To form the buffer layer of an Ag single crystal thin film excellent in surface flatness between the artificial metal lattice and a substrate at the time of forming the thin film on the substrate of MgO or Si by ion-beam sputtering by keeping the subtrate at a specified temp. CONSTITUTION:An ion-beam sputtering system is used to laminate an Ag (100) single crystal film 2 on an Si (100) or MgO (1 00) substrate 1 and an Ag (111) single crystal film on an Si (111) substrate 1. A vacuum chamber 10 is provided with a Kaufmann-type ion source 11, and an Ag target 5 is sputtered. The divergence field of the sputtered particles 5' is limited by a top plate 6, a shutter is opened or closed while monitoring the film thickness by the shutter 7 and quartz-resonator film thickness meter 8 driven from outside the vacuum chamber to keep the substrate at 50-250 deg.C, hence the (100) and (111) silver single crystal thin film excellent in surface flatness is obtained, and an artificial metal lattice having a better characteristic than before is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a buffer layer of a metal artificial lattice having a composition modulation structure.

(Prior Art) Epitaxial growth of silver thin films has been attracting attention and research due to academic interest in its surface structure and growth conditions, or due to its low electrical resistance. For example, A on a 5i (111) substrate
Example of fabricating g(111) by electron beam evaporation and evaluating its crystallinity by reflection high-energy electron diffraction (RHEED) (Japanese Journal of Applied Physics (J, J, A, P,) Vol. 17, No. 22 No. 2
(p. 097), Ag(100) was prepared by vapor deposition on a 5i(100) substrate cleaned with hydrofluoric acid at a substrate temperature of room temperature,
Example of evaluating its crystallinity by low-speed electron diffraction (LEED) (Japanese Journal of Applied Physics (J, J, A, P,) Volume 16, No. 3, 51
(p. 9), or an example in which Ag (111) was fabricated on pleated mica by vapor deposition at a substrate temperature of 550°C (Thin 5solid Films).
Volume 81, page L93).

(Problems to be Solved by the Invention) In order to enhance the effects of special properties such as perpendicular magnetic anisotropy in a metal artificial lattice, it is often necessary to improve the crystallinity of the artificial lattice.

However, it is not always easy to grow a metal superlattice with good crystallinity on a substrate. In that case, it is effective to provide a single crystal buffer layer with good surface flatness between the substrate and the metal superlattice.

An object of the present invention is to provide a buffer layer of a silver single-crystal thin film with good surface flatness between a metal superlattice and a substrate.

(Means for Solving the Problems) The present invention provides (1) formation by ion beam sputtering on a magnesium oxide (100) substrate or a silicon (100) substrate at a substrate temperature of 50°C or more and 250'C or less; (2) A method for producing a silver (100) single crystal thin film, characterized in that the silver (100) single crystal thin film is formed by ion beam sputtering on a silicon (111) substrate at a substrate temperature of 50° C. or higher and 250° C. or lower. 111) A method for producing a single crystal thin film, and (3) a method for producing a silver (100
) to silver (111) This is a method for producing a metal superlattice, characterized by forming two types of metals alternately on a single crystal silver film.

(Example) The present invention will be described below with reference to Examples. 1 and 2 are schematic diagrams of the chain wheel crystal thin film of the present invention. 5
i(100), or Ag(100) on MgO substrate 1
) single-crystal film 2 is formed on a 5i (111) substrate 1.
1) are laminated. In the present invention, an ion beam sputtering apparatus shown in FIG. 3 was used. The vacuum chamber 10 is equipped with a Kauffman type ion source 11 and sputters an Ag target 5. The sputtered particles 5' have a divergent field of view restricted by the top plate 6, and the film thickness is monitored by a shutter 7 and a crystal resonator film thickness meter 8 driven from outside the vacuum chamber.
g A thin film is formed. 9 is a heater, 12 is a vacuum pump, 13 is a gate valve, and 14 is a substrate holder. At this time, the degree of vacuum in the chamber is lXl0 'torr,
60 rpm on the substrate to avoid film thickness distribution within the substrate plane.
It gives a rotation of The output of ion source 4 is 600v, 2
At 0 mA, the Ag film formation rate was 0.2 A/see.

Under the above conditions, first, Mg0 (100) was used as the substrate, the substrate temperature was from -50℃ to 600℃, and the temperature was 1500A.
A thin silver film having a thickness of 100 ml was prepared, and the crystallinity of each film was examined by X-ray diffraction and reflection high-energy electron diffraction (RHEED). The results of X-ray diffraction at a substrate temperature of 150° C. are shown in FIG. 4, and the electron micrographs are shown in FIGS. 6(a) and (b).

The two RHEED patterns in Figure 6 are 45 degrees apart from each other and have a 4-fold symmetry, and Figure 6(a) is (1
10), FIG. 6(b) is seen from (100).

When considered together with the results of X-ray diffraction in which a sharp Ag (200) peak was observed, it can be seen that a (100) single crystal thin film of silver was formed. From the width between the streaks as seen from (110), the (110) lattice spacing of silver is 2.88A, (1
The (100) lattice spacing of silver is 4.08A based on the width between the streaks when viewed from 00). It was also found that this film had good flatness because the pattern shown in FIG. 6 consisted of streaks and the surface was a mirror surface. Silver (100) single-crystal thin film with good flatness has a substrate temperature of 50°C to 25°C.
Obtained only between 0°C. On the other hand, when the substrate temperature was lower than 50° C., the silver thin film was polycrystalline. Also, 250℃
The sample prepared at a higher temperature was a (100) single crystal thin film, but the sample surface was cloudy and the surface flatness was poor. Also,
Similar results were obtained when using a 5i (100) substrate that had been cleaned with hydrofluoric acid. Note that if a silver thin film is produced on a 5i (100) substrate without hydrofluoric acid cleaning, a part of the surface may become cloudy and the flatness may deteriorate.

Next, using 5i (111) that had been cleaned with hydrofluoric acid as a substrate, the substrate temperature was set at 150°C to 600°C.
A silver thin film with a thickness of 0A was prepared, and X-ray diffraction and RHEE
The crystallinity of each film was examined using D. Substrate temperature 1
The results at 50°C are shown in Figure 5, and the electron micrograph is shown in Figure 7.
Shown in Figures (a) and (b). The two patterns in FIG. 7 are 30 degrees apart from each other and have six-fold symmetry, and FIG. 7(a) is seen from (110) and FIG. 7(b) is seen from (221). When considered together with the results of X-ray diffraction in which a sharp Ag (111) peak was observed, it can be seen that a (111) single crystal of silver is formed. (110) and (22
1) The (110) lattice spacing of silver from the convergence between streaks is 2.88A. It was found that this film had good flatness because the pattern shown in FIG. 7 consisted of streaks and the surface was a mirror surface. A silver (111) single crystal thin film with a mirror surface with good flatness is produced at a substrate temperature of 50'C to 25°C.
Obtained only between 0'C. On the other hand, when the substrate temperature was lower than 50° C., the silver thin film was polycrystalline. Further, although the sample prepared at a temperature higher than 250'C was a (111) single crystal thin film, the sample surface was cloudy and the surface flatness was poor.

Note that if a silver thin film was produced on a 5i (111) substrate without hydrofluoric acid cleaning, a part of the surface would become cloudy and the flatness would deteriorate.

Next, the silver star crystal thin film with good flatness prepared in this way, Co/
Pd and Co/Au superlattices were prepared, and the perpendicular magnetic anisotropy energy was determined using a VSM and a torque magnetometer, and Mg0
A comparison was made with cases in which Co/Pd artificial lattices were directly fabricated on (100), 5i (100), and 5i (111) substrates. The Co/Pd and Co/Au artificial lattices were all fabricated by binary ion beam sputtering.
The O layer is 3A, the Pd layer or Au layer is 60A, and the repetition period is 40 times. The results are shown in Tables 1 and 2.

As shown in Tables 1 and 2, by using a silver single-crystal thin film as a buffer layer, it is possible to obtain perpendicularly magnetized films with high perpendicular magnetic anisotropy energy and good characteristics for both Co/Pd and Co/Au. was completed. In addition, in Co/Pd, Ag(111
) is more effective than Co/Au, Ag(100) is more effective.

(Effects of the Invention) As explained in the examples above, according to the present invention, silver star crystal thin films of (100) and (111) with good surface flatness can be obtained, and by using this as a buffer layer. , it is possible to produce a metal artificial lattice with better properties than conventional ones.

[Brief explanation of the drawing]

FIGS. 1 and 2 are schematic diagrams showing the structure of the single crystal silver thin film of the present invention. FIG. 3 is a schematic diagram of an ion beam sputtering apparatus used to carry out the present invention. Figure 4 is an X-ray diffraction diagram of the Ag thin film fabricated on the Mg0 (100) substrate, Figures 6 (a) and (b) are its electron micrographs, and Figure 5 is the Ag thin film fabricated on the 5i (111) substrate. The X-ray diffraction diagram of the Ag thin film, and FIGS. 7(a) and (b) are its electron micrographs. In the figure, 1 is a Si or MgO substrate, 2 is an Ag single crystal film, 5 is a target, 7 is a shutter, 1o is a vacuum chamber, and 11 is an ion source.

Claims (3)

[Claims] (1) On a magnesium oxide (100) substrate or silicon (100) at a substrate temperature of 50°C or more and 250°C or less
A method for producing a silver (100) single crystal thin film, the method comprising forming a silver (100) single crystal thin film on a substrate by ion beam sputtering. (2) A method for producing a silver (111) single crystal thin film, which is characterized in that it is formed on a silicon (111) substrate by ion beam sputtering at a substrate temperature of 50° C. or higher and 250° C. or lower. (3) Silver (1
00) or silver (111) single crystal film is formed, and two types of metals are alternately formed on this silver film.