We studied the microcrystalline and nanocrystalline silicon thin films by means of Raman spectroscopy technique. The applied external electric field causes the changes in the electric dipoles’ orientations to compensate the external field, and migration the atom of impurities, such as hydrogen, and point defects. The Si-O dipoles play the most significant role because of electron affinity for oxygen. Phonon eigen-frequencies 480 cm-1 for amorphous silicon Raman spectra around and 520 cm-1 for crystalline TO and LO modes are varied in their energy positions because of wide spread in bonding variation for Si and O atoms, types of dipoles for different point defects and isotopic variations. It is assumed that the nanocrystals which have grain boundary with oxygen atoms incorporated into silicon were destroyed in their crystal structure by Si-O dipoles reorientations caused by applied field. The initial crystal orientation was (111). The incorporated oxygen atoms are adsorbed in determined places. Their position results the appearance of numerous dangling bonds which are multiplied by the electric field and create the deep cracks in crystals. The crystal order is damaged along the axis that is perpendicular to (111). It is supposed that the microcrystal is a fractal structure on 2D plane.
SHG spectra from silicon films with different average size of nanocrystals were studied as possible
material for active channel in nonlinear optical switches. It is seen the spectral peak with energy 3.26 eV is
related to defects appeared in interface area silicon-silicon dioxide. For films with small silicon crystals
(less than 20 nm) the nonlinear optical response contains two spectral peaks. The second peak is caused by
optical response from nanocrystal grain boundary that contains oxygen atoms incorporated in silicon as
dipoles inside film. The optical nonlinear switch device based on the nonlinear optical response of SiOx
media inside film was proposed. Also, the silicon film with quartz micro-clusters was investigated as
material for making the nonlinear optical transmitter device. The PL spectra of films were, also, studied to
observe the various silicon and silicon dioxide fractions. The efficiency of transmission of radiation is
sufficient.
SHG spectra from silicon films with different average size of nanocrystals was studied as possible material for active
channel in nonlinear optical switches. It is seen the spectral peak with energy 3.26 eV is related to defects appeared in
interface area silicon-silicon dioxide. For films with small silicon crystals (less than 20 nm) the nonlinear optical
response contains two spectral peaks. The second peak is caused by optical response from nanocrystal grain boundary
that contain oxygen atoms incorporated in silicon as dipoles inside film. The optical nonlinear switch device based on the
nonlinear optical response of SiOx media inside film was proposed. Also, the silicon film with quartz micro-clusters were
investigated as material for making the nonlinear optical transmitter device. The PL spectra of films were, also, studied
to observe the various silicon and silicon dioxide fractions. The efficiency of transmission of radiation is sufficient.
We propose the infrared (IR) device based on polycrystalline silicon layers what differ in sizes of crystals. Such
crystals incorporate into different spatial structures: multilayer structure with several layers of silicon crystals and
conglomerates of large microcrystals surrounded by very small nanocrystalline layer. The differentiation in spatial
structure results in different electrical signal propagation and photon detection. It can be applicable for sensor and
microscale spectroscopic devices design. Hierarchical structures of grown thin silicon film with small and large
nanocrystals we can create new photon detector with redistribution of electrical signal according to applied potentials to
various silicon layers. The ratio surface/volume for small nanocrystals is high, but the surface area is small, but for large
crystals is opposite situation: the small value of ratio surface/volume and large area of surface. Because, there are many
small silicon nanocrystalls are bonded with one large silicon crystal. One such node of polycrystalline silicon film can be
used for nanoscale device making. Such kind of device is combined as photon detection by nanocrystals and electrical
signal distribution by single structural node according to the famous logical rules.
The manufacturing of nanoscale devices with sizes smaller than 100 nm is founded on the quantum physical phenomena. We proposed the new nanoscale device with photoacoustic switching. The memory cell can be made by means of two thin silicon surface layers one of which contains oxygen in Si-O-Si bonding. The charge storage is caused by inserting on clean silicon layer the oxygen incorporated with silicon. The mechanical deformation of upper oxidized silicon layer results in shift of atomic positions. The oxygen appearance on the silicon surface is reflected on electronic structure as new defect level inside band gap. The electrons are stored on this oxygen related level with energy position Ec-0.18 eV. By applied bias voltage we realize the erase procedure by removing the stored electron. The silicon surface should be prepared because the oxygen incorporation depends on the chemical properties. The electronic structure of oxidized silicon surfaces with (111) and (100) orientation was tested by using second harmonic generation response. The characteristic time of storage, 1 ns, was measured by using the laser time-resolved short pulse spectroscopy. We used modelocked mode of laser system with pulse duration 120 ps. The speed of switching was approximately 1013 Hz.
The design of quantum logical elements based on nanocrystalline silicon was made. The optical properties of polycrystalline silicon films with oxygen incorporation in grain boundary were experimentally studied. The Raman scattering, photoluminescent and Fourier-transformed infrared spectra were measured. The different kinds of defects were detected. The E' and D centers was measured by electron-spin resonance method. The triplet state of oxygen was detected by fourier-transform infrared spectroscopy. The hyperfine structure of oxygen level in A-center was detected by laser picosecond spectroscopy. It is assumed that the splitting of oxygen level is caused due to the ultrasound oscillation of oxygen atom in A-center. We propose the qubit based on A-centers in polycrystalline oxidized silicon.
The optical properties of polycrystalline silicon films with oxygen incorporation in grain boundary were experimentally studied. The Raman scattering photoluminescent and Fourier-transformed infrared spectra were measured. The morphology of the films were studied by atomic force microscopy. The strong correlation between the oxygen content and optical properties, and polarization was found. The oxygen diffuse incorporation corresponds the energetic levels in band gap around Ec-0.27 eV. The thermal annealing of polycrystalline film by the temperature more than 150° C produces the siloxane bonding with defect level in energy diagram near Ec-0.14 eV. The quantum beats of intensity of optical and electronic signal due to the quantum interference of closed electronic states was studied.
Silicon crystallites produced by low temperature plasma- enhanced chemical vapor deposition technique have been shown size-dependent photoluminescent and second harmonic generation responses. The crystalline volume fraction was estimated by using Raman spectra. The grain sizes of crystallites were measured by using x-ray diffraction. The structural chemical properties of poly-Si films were studied by means of Fourier-transform infrared spectroscopy and transmission spectrophotometry. The size- and shape- dependent second-harmonic generation of poly-Si films is, also, studied. The second-harmonic generation intensity for poly-Si deposited by using SiH4/SiF4/H2 gas mixture as function of such deposition conditions as hydrogen flow rate, silicon tetrafluoride flow rate, deposition temperature was studied.
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