RU2535244C1 - Tin ion-implanted silicon oxide film on silicon substrate - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: tin ion-implanted silicon oxide film on a silicon substrate includes alpha-tin nanoclusters. The film has thickness of 80-350 nm, average tin concentration in the range of 2.16 to 7.1 at % and the alpha-tin nanoclusters have a radius of 1.5 to 4 nm.

EFFECT: film has higher intensity and a short photoluminescence bandwidth.

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Description

The invention relates to materials science, to films of silicon oxide on a silicon substrate implanted with tin ions, and is intended for the development of functional elements of nano- and microelectronics, optoelectronics and nanophotonics. Such functional elements can be used to create instruments and devices for recording, displaying and converting information, for example, as photosensors of signaling devices in information systems, as elements of fiber technology and integrated optics, namely, microminiature light sources and short-wave radiation converters in long wave radiation.

Closest to the proposed film is a tin ion implanted silicon oxide film on a silicon substrate having a thickness of 500 nm and containing alpha-tin nanoclusters with an average radius of not more than 5 nm [Surface, X-ray, synchrotron and neutron studies, 2012, No. 8, p. 44-49].

The disadvantage of the prototype material is the reduced photoluminescence intensity and the broadened band of the photoluminescence spectrum in the range of 700 ÷ 1100 nm.

The objective of the invention is to increase the intensity of photoluminescence in the range of 700 ÷ 1100 nm and reduce the bandwidth of the photoluminescence spectrum in this range.

To achieve this task, a silicon oxide film implanted with tin ions on a silicon substrate, including alpha-tin nanoclusters, is characterized in that the film thickness is in the range 80–350 nm, the average concentration of tin is in the range from 2.16 to 7.1 atomic percent , alpha-tin nanoclusters have a radius of 1.5 to 4 nm.

The technical result when using the proposed film as a nanostructured material is to increase the photoluminescence intensity in the luminescence band 700 ÷ 1100 nm (1.13 ÷ 1.77 eV) by four times and narrowing the photoluminescence band by 1.24 ÷ 1.45 times. This is ensured by the presence in the proposed film of the above set of parameters: film thickness, average tin concentration in it, and sizes of alpha-tin nanoclusters. In this case, alpha-tin nanoclusters with a radius of 1.5 to 4 nm exhibit the properties of quantum dots with quantum confinement effects, which determine the variability and achievement of the required electron-optical properties of the nanostructured material.

When the above parameters of the proposed material (film thickness, average tin concentration and average radius of alpha-tin nanoclusters) exceed the limits specified in the claims, the increase in the intensity of photoluminescence and the narrowing of the bandwidth of the photoluminescence in the range 700 ÷ 1100 nm are not provided. This is due to the following reasons.

If the sizes of alpha-tin nanoclusters are less than 1.5 nm, the structure of the material degrades and the luminescent properties of the proposed material deteriorate due to an increase in the number of structural defects that are centers of luminescence quenching. The intensity of photoluminescence decreases, its band expands.

When the sizes of alpha-tin nanoclusters are more than 4 nm, the luminescence band shifts to the low-energy region, the luminescence intensity decreases, and the photoluminescence band expands. In addition, the technology of obtaining the proposed material is complicated, the use of an ion source with increased energy and an increase in implantation time are required, which is not economically feasible.

If the average concentration of tin is less than 2.16 atomic percent, the photoluminescence intensity decreases, a longer heat treatment is required to obtain clusters with sizes of 1.5-4 nm.

At an average tin concentration of more than 8 atomic percent, the effects of concentration quenching begin to appear and the sizes of nanoclusters increase.

If the film thickness is less than 80 nm, a sufficient degree of reproducibility of the technical result of the obtained silicon oxide film is not achieved due to the increased influence of the properties of the silicon substrate on the properties of the film, violations of the structure of the film-substrate interface, excessive increase in the density of radiation defects of the film (E'-centers, ODC centers , centers on non-bridge oxygen atoms, etc.). At the same time, obtaining the required sizes of alpha-tin nanoclusters and increased luminous intensity is not ensured.

With a film thickness greater than 350 nm, the duration of the process of ion implantation increases, which leads to an increase in the size of alpha-tin nanoparticles, and the number of radiation defects in the film structure increases. As a result, there is a partial quenching of photoluminescence, an expansion of the photoluminescence band and its shift to the long-wavelength region. The expansion of the photoluminescence band causes a decrease in intensity in the wavelength range of 700 ÷ 1100 nm.

In figures 1 and 2 presents the parameters of the proposed material.

Figure 1 - distribution of the concentration of tin (vertical axis, atomic percent - at.%) Over the film thickness of the proposed material (horizontal axis, nm) with a film thickness of 250 nm and an average tin concentration of 2.3 at.%.

Figure 2 - emission spectrum of the proposed material (vertical axis - photoluminescence intensity, relative units, horizontal axis - radiation wavelengths, nm) with a film thickness of 250 nm and an average tin concentration of 2.3 at.%.

The photoluminescence spectrum shown in FIG. 2 within 700 ÷ 1100 nm was obtained by excitation in the range of 77.5 ÷ 335 nm (3.7 ÷ 16 eV), in particular, with a DTL-394QT or DTL-389QT laser (Russia, Laser Compact) ) with a wavelength of 263 nm [http://www.laser-compact.ru]. Registration was performed using an ARC Spectra Pro-308i monochromator (0.3 m) and an R6358P photomultiplier (Hamamatsu).

The proposed tin ion implanted silicon oxide film on a silicon substrate, containing alpha-tin nanoclusters, is obtained from a finished material, which is a SiO ₂ film with a thickness of 80 ÷ 350 nm, thermally grown on a silicon substrate and processed in the following way:

- the SiO ₂ film is irradiated with Sn + tin ions in a continuous mode at an ion energy of 80 to 350 keV and a fluence of (5.0 ± 0.5) × 10 ¹⁶ ion / cm ^-2 ;

- after ion implantation, the film is annealed at a temperature of 850 ÷ 950 ° C for 30 ÷ 45 minutes in an atmosphere of dry nitrogen.

Tin ions were implanted into the obtained SiO ₂ film using an ion source operating in a continuous mode at a vacuum of (1.4 ÷ 2.5) × 10 ^-4 Topp. Granulated tin with a purity of 99.6% was used as the cathode of the ion source, and samples of a silicon oxide film on a silicon substrate washed with alcohol in an ultrasonic bath were used as the anode. Annealing was carried out in an electric resistance furnace (type NT 40/16).

The obtained samples of the proposed material — a silicon oxide film implanted with tin ions on a silicon substrate — are plane-parallel plates with an area of 1 cm ² , a thickness of 3 mm, and a surface of optical quality. The surface layer of each sample includes alpha-tin nanoclusters, the substrate of the sample is a silicon single crystal with an orientation of (100).

The table shows examples of the proposed material (samples No. 2 ÷ 4), as well as examples of two other materials (samples No. 1 and 5), the composition and structure of which do not correspond to the composition and structure of the proposed material.

The photoluminescence spectrum of sample No. 3 of the proposed material is shown in figure 2. The luminescence spectra of the remaining samples in shape correspond to the spectrum of sample No. 2, differing in the radiation intensities and bandwidth indicated in the table.

Table No. p / p Silicon Oxide Film Thickness (nm) Ion energy, fluence (keV; ion / cm ^-2 ) Annealing temperature and time (° С; min) Average tin concentration and sizes of alpha-tin nanoclusters (at.%; Nm) The radiation intensity at a wavelength of 870 nm, the bandwidth of the spectrum at the level of 0.5 (relative units; nm) one 70 65 750 10.7 15630 5 × 10 ¹⁶ thirty one 130 2 120 110 850 7.1 45450 5 × 10 ¹⁶ 80 2 172 3 250 240 910 3 87650 5 × 10 ¹⁶ 120 2.6 185 four 350 300 950 2.2 56110 5 × 10 ¹⁶ 160 3.9 201 5 380 340 1100 2 18920 5 × 10 ¹⁶ 90 5 250

The maximum intensity of photoluminescence of samples No. 2 ÷ 4 of the proposed material at a wavelength of 870 nm are in the range of 45450-87650 relative units The maximum intensity of photoluminescence of samples No. 1 and 5 of materials whose parameters are outside the range of the proposed material are 15630 and 18920 relative units, respectively, which is approximately four times lower than the glow intensity of the proposed material. The bandwidth of the spectrum at the level of 0.5 samples No. 2 ÷ 4 of the proposed material is in the range 172 ÷ 185 relative units The bandwidth of the spectrum of the sample No. 5 of the material, the parameters of which go beyond the proposed material, is equal to 250 rel.ed., that is, the bandwidth of the spectrum of the glow of the proposed material is 1.24 ÷ 1.45 times less than the bandwidth of the spectrum of the material according to the prototype.

Claims (1)

A silicon oxide film implanted with tin ions on a silicon substrate, including alpha-tin nanoclusters, characterized in that the film thickness is 80 ÷ 350 nm, the average concentration of tin is in the range from 2.16 to 7.1 atomic percent, alpha-tin nanoclusters have radius from 1.5 to 4 nm.

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