高温退火后非掺杂磷化铟材料的电子辐照缺陷

对不同气氛下高温退火非掺杂磷化铟(InP)材料的电子辐照缺陷进行了研究. 除铁受主外，磷化铁(FeP₂)气氛下退火后的InP中辐照前没有深能级缺陷，而辐照后样品的热激电流谱(TSC)中出现了5个较为明显的缺陷峰，对应的激活能分别为0.23 eV, 0.26 eV, 0.31 eV, 0.37 eV和0.46 eV. 磷(P)气氛下退火后InP中的热生缺陷较多，电子辐照后形成的缺陷具有复合体特征. 与辐照前相比，辐照后样品的载流子浓度和迁移率产生显著变化. 在同样的条件下，经FeP₂ 气氛下高温退火后的InP样品的辐照缺陷恢复速度较快. 根据这些现象分析了缺陷的属性、快速恢复机理和缺陷对材料电学性质的影响. 关键词： 磷化铟 电子辐照 缺陷     

Extended vacancy-type defects in silicon induced at low temperatures by electron irradiation

We have observed the formation of extended defects in silicon at low temperatures (below 25 K) by means of in-situ high-resolution transmission electron microscopy (HRTEM). The defects are distorted spheres, occasionally truncated by facets, less than 5 nm in diameter. These defects are stable up to 773 K, and they gradually shrink during annealing in the temperature range from 773 to 973 K. From the analysis of HRTEM images of the defects, we have suggested that the defects are voids formed via athermal migration of vacancies under electron irradiation.     

Optical detection of conduction electron spin resonance in InP

Conduction electron spin resonance is optically detected in InP at 1.7 K. The measured value |g¹| = 1.26 ± 0.05 is in very good agreement with theoretical predictions and with the only other experimental determination available.     

碳化硅中氦离子高温注入引入的缺陷及其退火行为的光谱研究

对氦（He）离子高温（600 K）注入6H-SiC中的辐照缺陷,在阶梯温度退火后演化行为的拉曼光谱和室温光致发光谱的特征进行了分析.这两种方法的实验结果表明,离子注入所产生晶格损伤的程度与注入剂量有关;高温退火导致损伤的恢复,不同注入剂量造成的晶格损伤需要不同的退火温度才可恢复.在阶梯温度退火下呈现出了点缺陷的复合、氦-空位团的产生、氦泡的形核、长大等特性.研究表明：高温（600 K）注入在一定剂量范围内是避免注入层非晶化的一个重要方法,为后续利用氦离子注入空腔掩埋层吸杂或者制备低成本、低缺陷密度的绝缘层 关键词： 6H-SiC 离子注入 拉曼光谱 光致发光谱     

The defects produced by electron irradiation in tellurium-doped germanium

Abstract

The nature of the irradiation induced defects in germanium single crystal doped with tellurium was studied by DLTS and electrical measurements.

The E_c-0.21 eV level produced by irradiation with 1.5 MeV electrons was studied by DLTS technique. It was found that the defect associated with the E_c-0.21 eV level is divacancy. The E-center like defect (group V impurity-vacancy pair) introduces the E_c-0.20 eV level in samples doped with group V impurity. The level introduced by tellurium (group VI impurity)-vacancy pair is located at deeper than E_c-0.21 eV.

The E_c-0.16 eV level was generated by the annealing at 430 K. A model for the defect associated with the level is proposed to be a tellurium-vacancies complex.     

Optical properties of Si-doped InAs/InP quantum dots

InAs quantum dots (QDs) were grown on InP substrates by low pressure-metalorganic chemical vapor deposition. Disilane (Si₂H₆) was used as an n-type dopant. The positions of Si doping were varied: buffer layer, capping layer, modulation doping, and QD itself. Surface treatment of InP by Si₂H₆ was also performed to see the effect of Si on InAs QD. Photoluminescence (PL) and atomic force microscopy (AFM) were used to characterize optical and structural properties of QDs, respectively. It was found that the PL peak positions varied from 0.73 to 0.88 eV with the position of Si doping. PL peak blue shift in modulation doped sample was explained in terms of state filling effect. It was found that Si doping at QD itself was the most effective way to obtain the strongest integrated PL intensity without degrading the QD size distribution.     

Photoluminescence of irradiation induced defects on CR-39

A gamma-irradiated poly allyl diglycol carbonate solid state nuclear track detector is studied by means of photoluminescence. The irradiation is done using a ⁶⁰Co cell with a dose rate of 7.5 kGy/h. Photoluminescent radiation is recorded with excitation radiation of wavelength 346 nm. A broad luminescent band shows a possible dosemetric property for γ-radiation in the dose range 0.1–8.0 MGy. High-dose irradiation by γ-rays introduces donor and acceptor levels in the forbidden energy gap. The broad band may be attributed to the number of overlapping emissions caused by transitions between these acceptor and donor levels.     

On the production of paramagnetic defects in silicon by electron irradiation

Monocrystalline silicon samples of different impurity contents have been irradiated with 1.5 MeV electrons in order to produce divacancies in their negative charge state. In these samples different combinations of defects have been observed with electron paramagnetic resonance. The conditions for production and observation of these defects are compared. For two new EPR spectra, labelled (Si-) NL11 and (Si-) NL12, the spin Hamiltonian parameters are reported. For NL11, which arises from an S = 1 spin state, the obvious identification with the neutral charge state of the divacancy can not be confirmed.     

Modification of Lexan polycarbonate induced by electron irradiation

An 8 MeV electron-induced modification of Lexan polycarbonate (Lexan) films has been studied systematically using UV–visible spectroscopy, LCR meter, X-ray diffractogram (XRD) and differential scanning calorimetry (DSC) techniques. The optical properties of the Lexan films showed a decrease in the optical energy gap with an increase in the electron dose. The AC conductivity and dielectric constant were found to change significantly due to irradiation, and the dielectric constant was found to obey the universal law of dielectric constant. The XRD results show that the crystallite size and the percentage of crystallinity of films decrease after irradiation. The decrease in glass transition temperature shown by DSC studies reveals that the polymeric system has changed towards a more disordered state.     

Structural transformations in carbon nanoparticles induced by electron irradiation

This paper reviews the electron-irradiation effects in graphitic nanoparticles. Irradiation-induced atomic displacements cause structural defects in graphite lattice forming the basis of carbon nanoparticles such as nanotubes or carbon onions. Defects of the type of non-six-membered rings induce topological alterations of graphene layers. The generation of curvature under electron irradiation leads to the formation of new structures, such as spherical carbon onions or coalescent nanotubes. At high temperatures, the self-compression of carbon onions can promote the nucleation of diamond cores or phase transformations of foreign materials that are encapsulated by onionlike graphitic shells. Under the nonequilibrium conditions of intense irradiation, the phase equilibrium between graphite and diamond can be reversed. It is shown that graphite can be transformed into diamond even if no external pressure is applied. All electron-irradiation and electron-microscopic studies described here were carried out using in situ transmission electron microscopy.     

Optical and electrophysical properties of defects in high-purity CdTe

The electronic spectrum of defects formed in low-temperature synthesis and growth of high-purity CdTe[111]from the vapor phase of the starting components has been studied by the photoluminescence and photoconductivity methods, as well as using the analysis of the behavior with temperature of the conductivity. The studies have revealed in the crystals, in addition to the comparatively shallow centers involving primarily donors and acceptors contained in residual substitutional impurities, deep acceptor states with activation energies of 0.25, 0.60, and 0.86 eV, which differ in the character and magnitude of the localizing potential. While the deep centers at 0.60 and 0.86 eV display strong localization of electronic states, the center with the 0.25-eV activation energy is associated with defects for which the major part of the localizing potential extends uniformly in space over several unit cells. Such centers are assumed to originate from twinning-induced extended defects.     

Optical properties of excitons in semiconductor (InP)-insulator quantum wires

Features in the spectra of absorption, luminescence, and luminescence efficiency obtained under sample excitation with differently polarized laser radiation, and the nonlinear dependence of the luminescence intensity on the excitation level are explained as due to excitonic transitions in semiconductor (InP)-insulator (chrysotile asbestos) quantum wires. The measured excitonic-transition energies in the quantum wires are in quantitative agreement with calculations. The calculations took into account both the size quantization in a quasi-one-dimensional structure and the “dielectric enhancement” of excitons (the noticeable increase of the exciton binding energy and of the excitonic-transition oscillator strength associated with the increased attraction between the electron and the hole due to the large difference between the dielectric permittivities of the semiconductor and the dielectric matrix).     

GaN厚膜中的质子辐照诱生缺陷研究

本文采用正电子湮没谱研究质子辐照诱生缺陷, 实验发现: 能量为5 MeV的质子辐照在GaN厚膜中主要产生的是Ga单空位, 没有双空位或者空位团形成; 在10 K测试的低温光致发光谱中, 带边峰出现了"蓝移", 辐照后黄光带的发光强度减弱, 说明黄光带的起源与Ga空位(V_Ga)之间不存在必然的联系, 各激子发光峰位置没有改变, 仅强度随质子注量发生变化; 样品(0002)面双晶XRD扫描曲线的半峰宽在辐照后明显增大, 说明质子辐照对晶格的周期性产生了影响, 薄膜晶体质量下降. 关键词： GaN 缺陷 质子 辐照     

Structure of defects in Pt induced by neutron and ion irradiation

The effect of formation of a nanocrystalline structure in the near-surface layer of platimun (99.99%) as a result of 30-keV Ar ion bombardment up to fluences of 10¹⁶–10¹⁷ cm^?2 was discovered by the direct method of field ion microscopy. The spatial distribution and structure of radiation damage in Pt was established in the case where Pt is bombarded by fast neutrons (E > 0.1 MeV) up to fluences of 6.7 × 10¹⁷ and 3.5 × 10¹⁸ cm^?2 in the RWW-2M reactor at a temperature of ～310 K.     

Phase change in CoTi2 induced by MeV electron irradiation

The phase change induced by MeV electron irradiation in the intermetallic compound E9₃–CoTi₂ was investigated using high-voltage electron microscopy. Under MeV electron irradiation, CoTi₂ was first transformed into an amorphous phase and, with continued irradiation, crystallite formation in the amorphous phase (i.e. formation of crystallites of a solid-solution phase within the amorphous phase) was induced. The critical temperature for amorphisation was around 250 K. The total dose (dpa) required for crystallite formation (i.e. that required for partial crystallisation) was high (i.e. 27–80 dpa) and, even after prolonged irradiation, the amorphous phase was retained in the irradiated sample. Such partial crystallisation behaviour of amorphous Co₃₃Ti₆₇ was clearly different from the crystallisation behaviour (i.e. amorphous-to-solid solution, polymorphous transformation) of amorphous Cr₆₇Ti₃₃ reported in the literature. A possible cause of the difference is discussed.     

Cathodoluminescence investigations of RIE-induced defects in InP

Cathodoluminescence (CL) measurements have been performed to characterize defects in InP created by reactive ion etching (RIE) in a CH₄/H₂/Ar plasma. Etching of semi-insulating InP:Fe leads to an increase of CL intensity. After etching of undoped, n-type InP a reduction of band-edge as well as band-acceptor/donor-acceptor-pair emission intensity is detected. No additional emission lines due to etching-induced defects have been detected in the spectral range examined. After a few minutes of electron beam injection the band-edge luminescence recovers to its initial value. Using donor-bound exciton emission, which is especially affected by RIE, mapping of these defects is possible, showing homogeneous defect distribution. In conjunction with other measurements (conductivity, photoluminescence, electron-beam-induced current, Raman scattering, Auger electron spectroscopy depth profiling) these results indicate a nonradiative, donor-like defect created by RIE.     

Electron irradiation induced defects in undoped and Te doped gallium phosphide

The aim of the present work is to investigate defects that are introduced to Gallium Phosphide (GaP) by electron irradiation as well as their dependence on the background doping. Undoped and Te doped n-type GaP have been irradiated with 1.5 MeV electrons at fluences of 5×10¹⁶ e/cm². Deep level transient spectroscopy assessment revealed the dependence of the trap characteristics on background doping.     

Creation of excitons and defects in a CsI crystal during pulsed electron irradiation

Data presented on the influence of the temperature in the range 80–650 K on the spectral kinetics of the luminescence and transient absorption of unactivated CsI crystals under irradiation by pulsed electron beams (〈E〉=0.25 MeV, t _1/2=15 ns, j=20 A/cm²). The structure of the short-wavelength part of the transient absorption spectra at T=80–350 K exhibits features, suggesting that the nuclear subsystem of self-trapped excitons (STE’s) transforms repeatedly during their lifetime until their radiative annihilation at T⩾80 K, alternately occupying di-and trihalide ionic configurations. It is established that a temperature-induced increase in the yield of radiation defects, as well as F and H color centers, and quenching of the UV luminescence in CsI occur in the same temperature region (above 350 K) and are characterized by identical thermal activation energies (∼0.22 eV). It is postulated that the STE’s in a CsI crystal can have a trihalide ionic core with either an on-center or off-center configuration; the high-temperature luminescence of CsI crystals is associated with the radiative annihilation of an off-center STE with the structure (I⁻(I⁰I⁻ e ⁻))*. Fiz. Tverd. Tela (St. Petersburg) 40, 640–644 (April 1998)