多孔硅吸收光谱和反射光谱

测定了多孔硅的吸收光谱和反射光谱，结果发现其吸收边对应于可见光区域。同单昌硅要比，其吸收边发生了蓝移，并且吸收强烈。由多孔硅反射谱曲一，利用Ｋ－Ｋ关系对其光学常数进行了简单的计算和分析。     

Characteristic features of the interaction of porous silicon with heavy water

The interaction of porous silicon (por-Si) with heavy water (D₂O) was investigated by means of time-resolved photoluminescence and infrared Fourier spectroscopy. It is shown that contact of por-Si with D₂O leads to anomalously rapid oxidation of its surface — at a rate at least an order of magnitude higher than the oxidation rate of por-Si in ordinary (protium) water. The oxidation process transforms the chemical composition of the por-Si surface and is accompanied by abrupt changes in the spectral and temporal characteristics of the photoluminescence. Assumptions are made concerning the nature of the interaction of porous silicon with heavy water. Fiz. Tekh. Poluprovodn. 32, 1016–1018 (August 1998)     

The effect of surface species on the photoluminescence of porous silicon

The photoluminescence of porous Si immersed in alcohol exhibits a blue shift and a marked decrease in intensity relatively to dry, as-anodized wafers. However, when the immersed samples are treated with ultraviolet (UV) light for a few minutes, the photoluminescence (PL) peak shifts to longer wavelength. Fourier transform infrared spectroscopy reveals that alkoxy surface species and silicon hydride species backbonded to oxygen atoms appear on the UV-treated samples. Furthermore, the PL characteristics and surface species of the UV-treated samples can be recovered to those of as-anodized wafers by dipping in hydrofluoric acid. These results point out the importance of surface chemistry in the luminescence process of porous Si.     

Relaxation spectra of photoluminescence from porous silicon obtained by chemical etching of laser-modified silicon

The distinctive features of time-resolved photoluminescence spectra of porous silicon created by chemical etching of single-crystal silicon subjected to modification by laser light has been investigated. Two bands were seen upon examination of the amplitude spectra: a band with a maximum at a wavelength (λ _max⋍530 nm) and a band with λ _max⋍420 nm and twice the intensity of the first. The relaxation curves are characterized by two sets of times: τ ₁<2×10⁻⁸ s and 2×10⁻⁸ s<τ ₂×10⁻⁴ s in the spectral ranges 420–700 nm and 500–850 nm, respectively. Upon increasing the energy density of the laser irradiation from ∼10 to ∼40 J·cm⁻², the intensity of the photoluminescence and the contribution of the fast component increased as well. The difference in the photoluminescence spectra compared to the spectra of layers of porous silicon obtained by electrochemical etching is attributable to a shift in the distribution of nanocrystallite sizes toward smaller sizes, which leads to an increase in the area of the Si/SiO_x surface that separates the phases. Although our results can be explained within the framework of a quantum-well model, we do not rule out the contribution of local centers at the Si/SiO_x phase boundary. The slow component of the relaxation is approximated by a “stretched” exponential. It is assumed that the slow component is controlled by the rate at which photocarriers leave the quantum-well nanocrystallites by tunneling through the Si/SiO_x barrier. Fiz. Tekh. Poluprovodn. 31, 6–10 (January 1997)     

Characterization of porous silicon carbide according to absorption and photoluminescence spectra

The results of the atomic-force microscopy, optical-absorption spectroscopy, and photoluminescence spectroscopy of porous silicon carbide (por-SiC) produced by anodic etching are reported. Analysis of the data shows that the cubic SiC phase is lacking in the porous layer and the photoluminescence signal from por-SiC at the excitation photon energy hν_ex ≤ E _g appears due to the formation of radiative centers associated with impurity atoms and surface defects produced upon anodic etching of the sample and subsequent treatment to uncover the pores.     

Rapid thermal oxidation of porous silicon for surface passivation

Rapid thermal oxidation with dry oxygen has been carried out on porous silicon (PS) films formed by electrochemical etching. The purpose of the paper was to investigate the surface passivation capability of the oxidized PS layers and to understand the oxidation mechanism. Rutherford back scattering (RBS) and X-ray photoemission spectroscopy (XPS) analyses confirmed the formation of a stoichiometric quasi-silicon dioxide. Besides, elastic recoil diffusion analysis (ERDA) demonstrated that a high concentration of hydrogen is still present in the PS film even after oxidation. RTO resulted in a good surface passivation effect at high temperature (>1000°C) as seen by internal quantum efficiency analysis. However, lifetime in bulk silicon is affected by the RTO process.     

Study of the deposition features of the organic dye Rhodamine B on the porous surface of silicon with different pore sizes

The deposition features of the organic dye Rhodamine B on the porous surface of silicon with average pore sizes of 50–100 and 100–250 nm are studied. Features of the composition and optical properties of the obtained systems are studied using infrared and photoluminescence spectroscopy. It is found that Rhodamine-B adsorption on the surface of por-Si with various porosities is preferentially physical. The optimal technological parameters of its deposition are determined.     

Characteristic features of Raman scattering of light in silicon doped with high krypton doses

A high-frequency 20-cm⁻¹ shift in the Raman spectrum of silicon implanted with krypton ions has been observed experimentally. The dynamics of the transformation of the microscopic structure of the surface layer of silicon was investigated on the basis of Raman scattering data obtained for different regimes of Kr⁺ implantation and laser annealing. The experimental data obtained by us are explained well by the presence of local mechanical stresses (∼40 kbar) due to the presence of heavy inert Kr atoms at the lattice sites. Fiz. Tekh. Poluprovodn. 31, 790–793 (July 1997)     

Characteristic features of the IR spectra of amorphous boron-doped hydrated silicon

Vibrational modes with wave numbers 1879 and 1848 cm⁻¹, previously observed only in the spectra of crystalline diborane, were observed in the optical spectra of a-Si:H(B) films. This indicates formation of complexes and bonds similar to those present in diborane, specifically, bridging hydrogen in the amorphous network. The change in the amplitudes of the observed modes after the films are annealed is attributed to structural rearrangements resulting in a decrease in the density of weakly bound bridging hydrogen and an increase in the density of quadruply coordinated boron. This explains the previously observed increase in the conductivity of annealed films. Fiz. Tekh. Poluprovodn. 32, 631–633 (May 1998)     

Special features of recombination of nonequilibrium charge carriers in porous silicon with different nanostructure morphologies

Photoluminescence of porous silicon with different nanostructure morphologies and silicon monocrystalline wafers used as substrates was studied comparatively. The photoluminescence intensity of mesoporous and nanoporous silicon was established to be related to the excitation intensity by the quadratic and linear dependences, respectively. A model of recombination processes in the semiconductor nanocrystal systems is suggested. The experimental results are in good agreement with the model predictions.     

Photoluminescence and photoexcitation spectra of porous silicon subjected to anodic oxidation and etching

The photoluminescence and photoexcitation spectra of porous silicon films with an initial porosity of 50–60%, produced on single crystals of p-type silicon and subjected to anodic oxidation and chemical etching, are studied. The existence of an amorphous phase in the etched porous silicon is found not to affect the photoluminescence spectrum of porous silicon. Features of the photoexcitation spectra before and after etching, as well as the evolution of the photoluminescence and photoexcitation spectra after etching, can be interpreted in terms of a uniform quantization model that includes elastic stresses in the silicon crystals of the porous silicon. Fiz. Tekh. Poluprovodn. 31, 1135–1141 (September 1997)     

Morphological evolution,Raman and photoluminescence spectra in optically transparent cubic silicon carbide

Optically transparent cubic SiC crystals were grown via atmospheric-pressure chemical vapour deposition (APCVD) on graphite substrates from methyltrichlorosilane (MTS) in hydrogen in a cold-wall RF induction furnace at temperatures from 1500 to 2000°C. The morphology of the crystals was correlated to substrate temperature, H₂/MTS ratio and hydrogen flow. Low-temperature photoluminescence (PL) spectra exhibited a zero-phonon line (2.3787 eV) attributable to an exciton bound to a neutral nitrogen donor, in addition to TA, LA, TO, and LO phonon replicas. The observed broadening and splitting of the PL spectral lines were associated with the morphological habit and internal strain of individual crystallites. Above about 1600°C preferential 〈110〉 growth directions were identified for the majority of the crystals. At intermediate deposition temperatures (1600–1700°C) the dominant morphology consisted of yellow prismatic crystals heavily twinned along {111} and {111¯}. At temperatures of about 1750°C hexagonally shaped {111}-oriented 3C-SiC platelets were formed with alternating {001}/{101} edges. A layer-by-layer growth model was used to rationalise the transition in preferred growth direction from 〈111〉 to 〈101〉 with increasing substrate temperature. © 1997 John Wiley & Sons, Ltd.     

基于不同单光子能量拉曼谱的氢化硅薄膜微观特性研究

用等离子体增强化学汽相沉积法（PECVD）在玻璃和单晶硅（c-Si）衬底上分别制备了氢化纳米硅（nc-Si：H）和非晶硅（a-Si：H）薄膜,用紫外、可见和近红外3种不同波长的激光线对不同形态的Si薄膜进行拉曼散射实验研究。研究发现,这些Si薄膜在不同的单光子能量的激光线激发下的拉曼谱线形也不同。进而通过对Si薄膜材料...     

Reversible and irreversible changes in the photoluminescence spectra of porous silicon held in water

The change induced in the photoluminescence spectra and photoluminescence excitation spectra by holding porous silicon in water is investigated. It is found that submerging a sample in water gives rise simultaneously to reversible and irreversible changes in the intensity and position of the photoluminescence maximum. It is shown that the irreversible changes are due to the same processes that occur in air: oxidation and desorption of substances which participate in the photoluminescence and which give rise to the visible-range band of the excitation spectrum, from the surface of the porous layer. It is established that the rate of these processes in water is much higher than in air. It is shown that the reversible changes are due to the vanishing of the visible-range photoluminescence excitation band in water. It is inferred that this band is attributable to water clusters that contain components of the etchant. Fiz. Tekh. Poluprovodn. 33, 1379–1383 (November 1999)     

Photoluminescence enhancement of porous silicon prepared with ammonium sulfide pre-treated silicon

As-grown porous silicon prepared with ammonium sulfide pre-treated silicon show stable photoluminescence characteristics due to high Si–N/PS interface quality and less damage PS with Si–N passivation. After aging in air for 6 months, it shows much stronger photoluminescence intensity and stable wavelength due to higher Si–ON/PS interface quality and less damage of PS with Si–O–N passivation from the oxidation of Si–N.     

Effects of surface passivation in porous silicon as H2 gas sensor

This paper investigates the effects of surface passivation in porous silicon (PS) as a hydrogen gas sensor. Two types of sample have been prepared, one with typical HF anodizing solution and the other with the presence of peroxide (H₂O₂) in the solution. The Fourier transform infrared (FT-IR) measurements on the PS layer on the Si substrate showed that the typical PS surface is characterized by chemical species like Si–H and Si–O. Samples anodized with peroxide based (H₂O₂) solution showed a PS structure with higher porosity (～80%) and better surface passivation (higher concentration of Si–O and Si–H species) compared to those not treated with peroxide. Peroxide based PS sample fabricated as an H₂ gas sensor showed better electrical (I–V) sensitivity compared to those without peroxide, which has been associated with good surface passivation. Surface passivation in peroxide based PS is also maintained at higher temperatures (100 °C).     

NH3／H2O2溶液腐蚀下多孔硅光致荧光

用光致荧光谱、傅里叶变换红外光谱（ＦＴＩＲ）和扫描电子显微镜（ＳＥＭ）对用阳极氧化法制成的多孔硅层在１％ＮＨ３／Ｈ２Ｏ２溶液中的腐蚀现象进行了研究。红外分析表明，Ｓｉ－Ｏ键和Ｈ－Ｏ键的强度随ＮＨ３／Ｈ２Ｏ２溶液的腐蚀时间的增加而增加，Ｓｉ－Ｈ键强主匠随腐蚀时间增加而减少。光致荧光谱的峰值在腐蚀开始时先下降后上升，半高宽变窄，谱峰的以边明显蓝移。分析研究表明，１％ＮＨ３／Ｈ２Ｏ２溶液对多孔硅层有腐蚀     

The optical second-harmonic generation from porous silicon

Second-harmonic generation from porous silicon with a magnitude of two orders greater than that from the original silicon crystalline wafers is discussed. The measured effective second-order nonlinear susceptibility X⁽²⁾_ps.eff for a p-type porous silicon is 1.96×10^-7 esu. The susceptibility is estimated on the base of a bulk property rather than on quantum confinement owing to its large surface to volume ratio     

食管癌患者血红蛋白表面增强拉曼散射光谱的统计分析

应用表面增强拉曼散射(SERS)光谱技术,以Ag纳米粒子为基底,对24例食管癌患者及20例健康人的血红蛋白样本进行了检测,并采用主成分分析(PCA)与判别分析方法对检测到的光谱数据进行分析。实验得到食管癌患者与健康人血红蛋白SERS光谱存在的区别反映了两组血红蛋白内部物质的含量差异,结果显示,与健康人相比,食管癌患者的血红蛋白中有更多的亚铁离子处于低自旋态。统计分析方法所得的光谱峰值PC得分的三维散点图对食管癌患者与健康人区别也较明显。本文方法的总准确率为91%,诊断灵敏度为96%,诊断特异性为85%。结果表明,通过血红蛋白SERS光谱的检测和统计分析,可为早期食管癌的诊断提供依据。     

Study of the processes of carbonization and oxidation of porous silicon by Raman and IR spectroscopy

Porous silicon layers were produced by electrochemical etching of single-crystal silicon wafers with the resistivity 10 Ω cm in the aqueous-alcohol solution of hydrofluoric acid. Raman spectroscopy and infrared absorption spectroscopy are used to study the processes of interaction of porous silicon with undiluted acetylene at low temperatures and the processes of oxidation of carbonized porous silicon by water vapors. It is established that, even at the temperature 550°C, the silicon-carbon bonds are formed at the pore surface and the graphite-like carbon condensate emerges. It is shown that the carbon condensate inhibits oxidation of porous silicon by water vapors and contributes to quenching of white photoluminescence in the oxidized carbonized porous silicon nanocomposite layer.