Study of interface traps from transient photoconductive decay measurements in passivated HgCdTe

Generation-recombination (g-r) processes in the passivant/HgCdTe interface region are shown to complicate the transient photoconductive (PC) decays. Anomalous PC decays showing delayed peaks are observed and modeled for the first time. These peaks are correlated with the electron and hole traps in the interface region. Activation energy and density of the electron traps in the anodic oxide/n-Hg_0.78Cd_0.22Te interface region are estimated to be 12 meV and 1.1×10¹⁰ cm⁻², respectively. Density of hole traps is estimated to be 2.4×10¹⁰ cm⁻².     

Capacitance transient spectra of processing- and radiation-induced defects in silicon solar cells

Capacitance transient spectroscopy is used to study defects in chips of fully fabricated silicon solar cells. Characteristic differences are observed as a function of the crystal growth type (crucible grown or float zoned) and dopant (boron or aluminum) of the starting material, processing variables (diffused or implanted junctions, electron beam or furnace annealing) and radiation environment (1 MeV electron irradiation).     

Characterization of structural defects in the silicon crystal grown with various seeds

To see the effect of the seeds on the crystallization of the silicon ingot, two types of seed were prepared and applied to the mono-like multi-crystalline silicon crystallization. One of them was conical shaped seed divided vertically into 4 pieces and the other one was chipped silicon seeds. Both of the seeds were placed at the bottom of the crucible before the growth of the multi-crystalline silicon material with a conventional directional solidification process. Compared to the conventional thin and flat seeds, conical shaped seed result in the larger single crystalline portion in the ingot although the gap of the seed division might act as source of dislocation generation during the crystal growth. This was expected to be due to the lateral growth of the silicon single crystalline grown from the conical seed which is taller than normal flat seeds. And also, comparison of the Minority Carrier Life Time (MCLT) between the silicon crystal grown from the chipped silicon seeds and the silicon crystal grown without any seed was conducted. It was found that the silicon crystal grown with chipped silicon seeds shows higher MCLT than the silicon crystal grown without seeds, although both crystals look similar as multi-crystalline silicon.     

基于激光热成像方法的奥氏体钢表面缺陷表征

有源热成像是当今广泛使用的无损检测方法,可利用材料热特性完成缺陷表征。本文使用激光作为热成像的激励源,使用激光局部加热试件,产生的球形热流允许以任意方向检测缺陷。在加热过程中,能量扩散完全覆盖缺陷区域,在散热过程中,缺陷的存在会使得激光器的热足迹呈现不对称性,红外热像仪实时监测表面温度场分布,实现表面缺陷的可视化检测。通过实验验证以及对实验结果的图像分析来完成缺陷表征,结果表明:在散热过程中,红外热像仪可实现对缺陷的可视化检测,通过图像锐化处理检测缺陷边界,得到缺陷的形状分布,完成缺陷的定位表征。     

Characterization of defects in hydrogenated amorphous silicon devices using charge collection scanning electron microscopy

Electron-beam-induced current (EBIC) and secondary electron image (SEI) modes of a scanning electron microscope (SEM) are utilized for characterization of charge collection inhomogeneities in hydrogenated amorphous silicon devices. These inhomogeneities are due to such fabrication defects as substrate surface roughness, pin holes, blistering and lift-off. SEM observations are correlated with the electrical properties of the devices. Electronirradiation-induced damage in these devices is also investigated by measuring the EBIC time decay at continuous electron irradiation as a function of both the electron -beam energy and current. This decay mechanism is based on the formation of electron-irradiation-induced microscopic defects that act as recombination centers and reduce the lifetime of carriers.     

Characterization of deep defects in boron-doped CVD diamond films using transient photocapacitance method

We have developed a highly-sensitive transient photocapacitance measurement (TPM) system for deep defects in wide bandgap materials, and applied it to characterize the boron-doped diamond films grown on a high-pressure/high-temperature-synthesized Ib diamond substrate using high-power-density microwave-plasma chemical vapor deposition method. The developed TPM system has both a low detection limit of less than 0.5 fF for changes in the photocapacitance and a low measurement temperature drift of less than 0.03 K in 12 h. By using the TPM system, we have successfully found an acceptor-type defect around 1.2 eV above the valence-band maximum for the B-doped diamond film with a considerably high crystalline quality that had some strong exciton emission peaks in the cathodoluminescence spectra taken at ≈80 K. The photoionization cross section and the defect density estimated for the observed defect were 3.1×10^–15 cm² and 2.8×10¹⁶ cm⁻³, respectively.     

Reaction pathways and sources of OH groups in low temperature remote PECVD silicon dioxide thin films

Silicon oxides deposited by remote plasma-enhanced chemical-vapor deposition (Remote PECVD) can be grown under conditions which produce hydrogen-free SiO₂, and under conditions which promote the incorporation of bonded-hydrogen in either SiH or SiOH groups, but generally not in both. In this paper, we investigate the relationship between the deposition conditions leading to OH incorporation, and other post-deposition pathway(s) by which OH can also be incorporated. Two ways by which OH can be incorporated into the oxides are by: (i)intrinsic pathways which are associated with the heterogeneous chemical reactions responsible for film growth; and (ii)extrinsic pathways which refer to incorporation after film deposition stops. The results of our experiments to date show no evidence to support the intrinsic process; all of the infrared (ir) detectable OH is shown to derive from post-deposition or extrinsic sources. We have found two distinct post-deposition sources, one from the deposition chamber ambient during cool-down and one from atmospheric moisture. Each of these sources has a particular spectroscopic signature. We show that OH incorporated from atmospheric moisture occurs as spatially correlated near-neighbor Si-OH groups, whereas OH groups incorporated in the deposition chamber ambient are randomly distributed in the SiO₂ host material.     

Characterization of adhesion property between fused silica and thermoplastic polymer film in thermal nanoimprint lithography using a novel pull-off test

A novel pull-off test that mimics the actual thermal NIL process was conducted to investigate the adhesion properties between a flat fused silica and thermoplastic polymer film used in thermal NIL process. The pull-off force was measured under various NIL conditions—such as use of various polymer materials, imprint pressures, and separation velocities—and the surfaces of the mold and polymer film were observed after the test. The anti-sticking layer (ASL) derived from (1H,1H,2H,2H-perfluorooctyl)trichlorosilane (F₁₃-OTS) was coated on the fused silica and its effects on the adhesion characteristics was also examined. In cases of the mold without ASL, the pull-off force varied significantly according to the process conditions and damage on the polymer film was observed in most of the tests. In cases of the mold coated with the ASL, on the other hands, the pull-off force was maintained at a lower level in the range of the imprint pressure from 2 to 10 MPa or separation velocity from 1 to 25 μm/s, and there was no damage to the polymer film due to adhesion.     

Characterization of the silicon nitride–thermal oxide interface in oxide–nitride–oxide structures by ELS, XPS, ellipsometry, and numerical simulation

This work studies the properties of the SiO₂-Si₃N₄ interface in oxide-nitride-oxide (ONO) structures by using energy loss spectroscopy, X-ray photoelectron spectroscopy, ellipsometry measurements and numerical simulation. By oxidation the as-deposited Si₃N₄, silicon-silicon bonds at Si₃N₄-thermal SiO₂ interface are found. These excess Si-Si bonds are produced by replacing nitrogen with oxygen during the oxidation of Si₃N₄. We further propose that the Si-Si bonds are the major trap center at the Si₃N₄-SiO₂ interface. With MINDO/3 numerical simulation, we have found that the Si-Si bonds can capture both electrons and holes at the top Si₃N₄-SiO₂ interface. These bonds are proposed to be the responsible candidate for the positive charge accumulation in re-oxidized nitrided oxide.