Structure and optical properties of silicon layers with GaSb nanocrystals created by ion-beam synthesis

We have studied the ion-beam synthesis of GaSb nanocrystals in Si by high-fluence implantation of Sb and Ga ions followed by thermal annealing. RBS, TEM/TED, RS, and photoluminescence (PL) were employed to characterize the implanted layers. It was found that the nanocrystals size increases from 5 to 60 nm in the samples annealed at 900 8Cup to 20–90 nm in the samples annealed at 1100 8C. An existence of significant mechanical stresses within implanted layers has been detected. The stress values have been calculated from the shift of the Si first order Raman band. For the samples annealed at 900 8C a broad band in the spectral region of about 0.75–1.05 eV is detected in the PL spectra. The nature of this PL band is discussed

Nanocrystal- and Dislocation-Related Luminescence in Si Matrix with InAs Nanocrystals

We have studied the influence of ion implantation and post-implantation annealing regimes on the structural and optical properties of silicon matrix with ion-beam synthesized InAs nanocrystals. (100) Si wafers were implanted at 25 and 500 ±C, subsequently with high fluences of As and In ions. After implantation the samples were processed by furnace and rapid thermal annealing at 900, 950 and 1050 ±C. A part of the samples implanted at 25 ±C was additionally exposed to H+2 ions (100 keV, 1.2 × 1016 cm−2 in terms of atomic hydrogen). This procedure was performed to obtain an internal getter. In order to characterize the implanted samples transmission electron microscopy and low-temperature photoluminescence techniques were employed. It was demonstrated that by introducing getter, varying the ion implantation temperature, ion fluences and post-implantation annealing duration, and temperature it is possible to form InAs nanocrystals in the range of sizes of 2–80 nm and create various concentration and distribution of di˙erent types of secondary defects. The last ones cause in turn the appearance in photoluminescence spectra dislocation-related D1, D2 and D4 lines at 0.807, 0.870 and 0.997 eV, respectively

Ion Beam Synthesis of InAs Nanocrystals in Crystalline Silicon

The formation of nanodimensional InAs crystallites on Si wafers was studied by the method of high fluence implantation of As and In ions with subsequent high temperature treatment. It was found that the size and depth distributions of the crystallites depend on both the implantation temperature and the annealing conditions. A broad band in an energy range of 0.75–1.1 eV was recorded in the photolumines cence spectra of the samples

Structure and Optical Properties of Silicon Layers with GaSb Nanocrystals Created by Ion-Beam Synthesis

We have studied the ion-beam synthesis of GaSb nanocrystals in Si by high-fluence “hot” implantation of Sb and Ga ions followed by thermal annealing. The Rutherford backscattering, transmission electron microscopy/ transmission electron di˙raction, Raman spectroscopy and photoluminescence were used to characterize the implanted layers. It was found that the nanocrystal size increases from 5 to 60 nm in the samples annealed at 900 ±C up to 20–90 nm in those annealed at 1100 ±C. For the samples annealed at 900 ±C a broad band in the region of 0.75–1.05 eV is registered in the photoluminescence spectra. The nature of this photoluminescence band is discussed

A New Nanoporous Material Based on Amorphous Silicon Dioxide

Processes for making nanoporous SiO2 layers on Si via the irradiation of thermally oxidized silicon wafers with fast ions followed by chemical treatment in a solution or vapor of hydrofluoric acid are presented. It is shown that the density, shape, diameter, and length to diameter ratio of channels etched in silicon dioxide can be controlled by varying the regimes of fast ion irradiation or chemical treatment of SiO2/Si structures. Track parameters calculated using the thermal spike model are compared with the chemical etching data

Structure changes in InP and GaAs crystals double irradiated with electrons and swift heavy ions

We have studied InP and GaAs crystal structure changes under the influence of swift Kr and Bi ions irradiation by means of scanning electron microscopy, atomic force microscopy and selective chemical etching. The previous disordering of samples by electron irradiation is shown to be leading to macrodefect formation in the form of cracks and breaks at the depths near the ion end-of-range and on the crystal surface. A possible explanation of the observed effects is proposed.Вивчено вплив змін структури ІnP і GaAs при опроміненні іонами Kr і Bі й електронами при вивченні методом електронної мікроскопії, атомної силової мікроскопії й сективного хімічного травлення. Основними ефектами при цьому впливі були утворення тріщин і руйнувань структури поверхні, які найбільше значно проявлялися наприкінці пробігу іонів і поблизу поверхні. Можливе пояснення виявлених ефектів представлено.Изучено влияние изменений структуры InP- и GaAs- при облучении ионами Kr и Bi и электронами при изучении методом электронной микроскопии, атомной силовой микроскопии и сективного химического травления. Основными эффектами при этом воздействии являлись образование трещин и разрушений структуры поверхности, которые наиболее значительно проявлялись в конце пробега ионов и вблизи поверхности. Возможное объяснение обнаруженных эффектов представлено

Raman study of light-emitting SiNx films grown on Si by low-pressure chemical vapor deposition

Si-rich silicon nitride (SRSN) films were deposited on Si wafers by low pressure chemical vapor deposition (LPCVD) technique and, subsequently, annealed at (800–1200) °C to form Si precipitates. The composition of SiNx films was measured by Rutherford backscattering spectrometry (RBS). Two sets of samples differed by the amount of excessive Si (Siexc) in silicon nitride were studied. Evolution of Si nanoclusters from amorphous to crystalline ones during high temperature treatment was examined by Raman scattering (RS) spectroscopy. The amorphous Si clusters were already revealed in as-deposited SiNx while the annealing results in their crystallization. The crystalline nanoprecipitates are only registered in nitride films after annealing at 1200 °C. A dependence of Raman scattering intensity from the Si wafer on the temperature of annealing of SiNx/Si structures was revealed. This information was used to explain the phase transformations in SRSNs during high temperature treatments. The peculiarities of photoluminescence (PL) spectra for two sets of Si-rich SiNx films are explained taking into account the contribution from the quantum confinement effect of Si nanocrystals and from the native defects in silicon nitride matrix, such as N- and K-centers

Процессы деградации электролюминесценции светоизлучающих структур на основе тонких пленок оксида и нитрида кремния

SiO2 /Si, SiN1.2/SiO2 /Si and SiO2 /SiN0.9/SiO2 /Si structures have been fabricated by chemical vapor deposition and thermal oxidation of silicon. The elemental composition and thicknesses of dielectric layers have been studied using Rutherford backscattering spectroscopy, scanning electron microscopy, and spectral ellipsometry. The electroluminescence (EL) of the samples has been investigated in the “electrolyte–dielectric–semiconductor” system at a positive bias voltage applied to the silicon substrate. An intense band with maxima at 1.9 eV appears on the EL spectra of the SiO2 /Si sample, while the EL spectra of the SiN1.2/SiO2 /Si and SiO2 /SiN0.9/SiO2 /Si samples are characterized by the presence of bands with the maximum values of 1.9, 2.3 and 2.7 eV. The nature of these bands is discussed. Passing a charge in the range of 100–500 mC/ cm2 through the SiO2 /SiN0.9/SiO2 /Si sample, an increase in the EL intensity was recorded in the entire visible range. Passing a charge of 1 C/cm2 through a sample with a three-layer dielectric film resulted in the EL intensity decrease. It can be explained by the upper oxide layer degradation. It has been shown that silicon nitride deposited on top of the SiO2 layer protects the oxide layer from field degradation and premature breakdown. The most stable electroluminescence when exposed to a strong electric field is observed for the structure SiN1.2/SiO2 /Si.Одно-, двух- и трехслойные светоизлучающие композиции SiO2 /Si, SiN1,2/SiO2 /Si и SiO2 /SiN0,9/SiO2 /Si изготовлены на кремниевых подложках p-типа методами химического осаждения из газовой фазы и термооксидирования кремния. Элементный состав и толщины диэлектрических слоев изучены методами резерфордовского обратного рассеяния, растровой электронной микроскопии и спектральной эллипсометрии. Для изучения электролюминесценции (ЭЛ) использовалась система «электролит–диэлектрик–полупроводник», регистрация спектров ЭЛ проводилась в гальваностатическом режиме при положительном смещении кремниевой подложки. На спектрах ЭЛ образца SiO2 /Si проявляется интенсивная полоса с максимумом 1,9 эВ, спектры ЭЛ образцов SiN1,2/SiO2 /Si и SiO2 / SiN0,9/SiO2 /Si характеризуются наличием полос с максимумами при 1,9, 2,3 и 2,7 эВ. Обсуждается природа этих полос. Пропускание через образец SiO2 /SiN0,9/SiO2 /Si заряда в диапазоне 100–500 мКл/см2 приводит к увеличению интенсивности ЭЛ всех регистрируемых полос. После пропускания через образец с трехслойной диэлектрической пленкой заряда величиной 1 Кл/см2 интенсивность ЭЛ уменьшается, что объяснено деградацией верхнего слоя оксида кремния. Проведенные исследования позволяют сделать вывод, что нитрид кремния, нанесенный поверх слоя SiO2 , предохраняет слой SiO2 от полевой деградации и преждевременного пробоя. Наиболее стабильной электролюминесценцией при воздействии сильного электрического поля характеризуется структура SiN1,2/SiO2 /Si