Reflection of keV heavy-ion beams from solid targets. Dependence on energy and angle of incidence

Recent experimental and theoretical studies of the reflection of keV heavy-ion beams have been extended to higher energies and to non-perpendicular incidence. The reflection coefficient for Na⁺ and K⁺ ions backscattered from polycrystalline gold and silver targets has been obtained for perpendicular incidence at energies of 100–500 keV. The dependence on angle of incidence has been investigated at 30 keV for the same combinations of targets and projectiles. Effects of electronic stopping have been included in the theoretical calculations. Good agreement between the experimental results and the theoretical calculations is found.     

Carrier removal by implanted IONS in GaAs

Abstract

A model for calculation of the range distribution of energetic ions with taking into account the channeling effect is proposed. The measurement of the depth distributions of boron ions in silicon crystals implanted at 13.6 and 91 MeV revealed significant difference between the measured and the calculated range profiles when the channeling effects have not been included in the calculation. In spite of deminishing the critical angles of channeling with growing ion energy the probability of the capture of ions into the channeling regime is significant in case of high energy implantation even when the incident angles are 7–10° off the main crystallographic directions.     

NaCl稀溶液结晶的分形形态研究

通过光学显微镜观察NaCl稀溶液在玻璃基底上快速蒸发结晶形成了完整的立方晶体、DLA凝聚体和形状复杂的凹凸状结晶3种形貌.对复杂的凹凸状结晶进行分析,认为不完整的NaCl小晶粒构成了一个个微小的生成元,以随机Koch曲线的生长方式自组织地顺次相互连接起来,指出此类结晶符合随机Koch曲线,是远离平衡态下的自组织现象.通过改变观测尺度求维数的方法,得到分形维数是1.15±0.06,与Koch曲线相近.     

X-ray diffraction on solid solutions with atoms of different sizes

The formula for intensity of diffraction of X-rays on random binary solid solution is derived using the linear model of rigid atoms of different sizes in close-packed arrangement. The shape and position of the peaks of diffuse scattering resulting as the main diffraction effect are influenced by different sizes of atoms. On the other hand, the integrated intensity of the diffuse peaks is practically unaffected by the size effect.     

Optical and X-ray diffraction studies of multilayer structures based on InGaN/GaN solid solutions

Multilayer structures based on the In _x Ga_{1 ? x} N/GaN compounds grown by gas-phase epitaxy from organometallic compounds are studied using photoluminescence spectroscopy and high-resolution X-ray diffraction. A method for analyzing the experimental rocking curves of multilayer structures in terms of the Parratt-Speriosu model is developed. This method permits one to determine the thickness, period, and average composition of In _x Ga_{1 ? x} N/GaN layers, as well as the deformation of the active region in the samples under study. The local indium content is determined using the theoretical model which describes the radiation energy as a function of the thicknesses of the InGaN layers taking into account the energy of quantum confinement, the energies of the spontaneous polarization and piezoelectric polarization, and the parameters determined from high-resolution X-ray diffraction data.     

White-beam X-ray diffraction and radiography studies on high-boron-containing borosilicate glass at high pressures

ABSTRACT

Multi-angle energy-dispersive X-ray diffraction studies and white-beam X-ray radiography were conducted with a cylindrically shaped (1?mm diameter and 0.7?mm high) high-boron-content borosilicate glass sample (17.6% B₂O₃) to a pressure of 13.7?GPa using a Paris-Edinburgh (PE) press at Beamline 16-BM-B, HPCAT of the Advanced Photon Source. The measured structure factor S(q) to large q?=?19 Å^?1 is used to determine information about the internuclear bond distances between various species of atoms within the glass sample. Sample pressure was determined with gold as a pressure standard. The sample height as measured by radiography showed an overall uniaxial compression of 22.5% at 13.7?GPa with 10.6% permanent compaction after decompression to ambient conditions. The reduced pair distribution function G(r) was extracted and Si–O, O–O and Si–Si bond distances were measured as a function of pressure. Raman spectroscopy of the pressure recovered sample as compared to starting material showed blue-shift and changes in intensity and widths of Raman bands associated with silicate and four-coordinated boron.     

Investigation of fill factor losses on 20.2% efficient n‐type mono‐like silicon solar cells with laser contact opening

Large area (243.36 cm²) back‐junction passivated emitter, rear totally diffused (PERT) solar cells with laser contact opening (LCO) on n‐type mono‐like crystalline Si with efficiencies of 20.2% are presented. Boron emitters with high electrical quality (implied open circuit voltage iV_OC up to 700 mV) are formed during a co‐diffusion step using SiO_x:B layers. Increasing the rear metal contact coverage, we observed a decrease in fill factor (FF) instead of the expected increase due to the decrease of the back side series resistance. We show that it can be attributed to recombination centers (RCs) in the space charge region underneath the contact spots inducing an increasing second diode contribution. The presented empirical model for the RCs implemented in Synopsys Sentaurus TCAD allows for a successful reproduction of the FF, pseudo FF and V_OC behaviour with contact coverage. According to this model, the RCs induced by laser ablation and subsequently evaporation of Al have a shallow exponential distribution with a characteristic length of L_T = 0.2 µm and an effective surface density of N *_T0 = 25 cm^–1. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Raman studies on the effect of multiple-energy ion implantation on single-crystal hexagonal boron nitride

Single energy ion implantation of hexagonal boron nitride (h-BN) at various fluences and keV energies has shown that there is a change in the local symmetry of the crystal from hexagonal to the cubic (c-BN) symmetry. These conclusions have been primarily based on Raman scattering (RS) and Fourier transform infrared spectroscopy. Transmission electron microscopy (TEM) analyses have been a challenge because the sample preparation for cross-sectional study of both the polycrystalline substrates and single-crystal material used in the study presented problems that were difficult to circumvent. A multiple-energy implant with different fluence fractions has been used to create a uniform implanted layer in the material from the surface to the end of range of the implant in this study. We report on the initial RS studies on these samples.     

磷离子注入速率对4H-SiC(0001)晶格恢复与电阻率降低的影响

高剂量的磷离子注入4H-SiC(0001)晶面，注入速率从1.0×1012到4.0×1012 P+ cm-2s-1变化，而注入剂量固定为2.0×1015 P+ cm-2。室温注入，1500oC的高温下退火。利用光荧光和拉曼谱分析注入产生的晶格损伤以及退火后的残余缺陷。通过霍耳测试来分析注入层的电学性质。基于上述测试结果，发现通过减小磷离子的注入速率，极大地减少了注入层的损伤及缺陷。考虑到室温注入以及相对较低的退火温度(1500 oC)，在注入速率为1.0×1012 P+ cm-2s-1及施主浓度下为4.4×1019 cm-3的条件下，获得了非常低的方块电阻106 Ω/sq。     

离子辐照对单晶Si中预注入B原子扩散的影响

室温下使用MeV能量级Si,F和O离子对5keV B离子预注入后的n-型单晶Si(100)进行了辐照,应用二次离子质谱仪测试分析了掺杂物B原子的分布剖面及其变化.结果表明,高剂量Si,F和O离子的附加辐照可以抑制热激活退火中B原子发生的瞬间增强扩散.在相同的辐照条件下,Si近表面区域中SiO₂层的存在更有助于限制B原子的瞬间增强扩散.结合卢瑟福沟道背散射分析和DICADA程序计算对实验结果进行了讨论.     

boldmath In situ high temperature X-ray diffraction studies of ZnO thin film

An epitaxial ZnO thin film was entirely fabricated by pulsed laser deposition. Both the orientation and the size of the crystallites were studied. The X-ray diffraction (XRD) patterns of the film show strong c-axis oriented crystal structure with preferred (002) orientation. The Phi-scan XRD pattern confirms that the epitaxial ZnO exhibits a single-domain wurtzite structure with hexagonal symmetry. In situ high-temperature XRD studies of ZnO thin film show that the crystallite size increases with increasing temperature, and (002) peaks shift systematically toward lower 2θ values due to the change of lattice parameters. The lattice parameters show linear increase in their values with increasing temperature.     

Nano structure of low crystallinity carbon materials analyzed by using high energy X-ray diffraction

In this study, we tried to characterize a kind of low crystallinity carbon materials. The structure of polyparaphenylene(PPP)-based carbon was analyzed by means of high energy X-ray diffraction using the apparatus of SPring-8. The experimental results revealed the existence of basic structural units (BSU) in the highly disordered materials like PPP-based carbon. It is thought that the PPP-based carbons consist of small turbostratic particles, which have a few piled up poly-aromatic layers. The structure of the PPP-based carbon which seemed to be amorphous was estimated to have hexagonal carbon layers with the size of up to 1 nm. The pores in the PPP-based carbon seem to be clearances formed among the BSUs and amorphous carbon. The pore size of PPP-based carbon was estimated from the result of N₂ absorption measurement. The experimental results suggested that the lithium ion charge mechanism in the PPP-based carbon differs from that in graphite.      

多层膜闪耀光栅衍射的运动学研究

用 X射线运动学理论对软 X射线多层膜闪耀光栅的衍射特性进行了详细的研究 ,得到了衍射规律的一般表达式 ,讨论了产生衍射极大值的条件、光谱特性 ,不同于光栅和多层膜的色散特性。以及用作软 X射线单色器的一般性问题。发现只要选择合适的光栅参数 ,便可以将衍射光的大部分能量集中到某一个非零衍射级上。     

X-ray diffraction evidence of the single solid solution character of bi-metallic Pt-Pd catalyst particles on an amorphous SiO2 substrate

An X-ray diffraction study was carried out on powders of a series of catalysts prepared from aqueous solutions of H₂PtCl₆ and PdCl₄ and amorphous SiO₂ with different concentrations in weight of Pt and Pd at about 4% in overall metallic weight. Measurements of the position of high angle Bragg reflections in the diffractograms show evidence of the fact that the small catalyst particles are bi-metallic Pt-Pd crystals having a face-centred cubic Bravais lattice. The lattice constant of these crystals was found to change with the relative concentration of Pt and Pd by following the Vegard’s rule. This correlation leads to the conclusion that the bi-metallic catalyst particles are made of a single solid solution of Pt and Pd atoms in the whole range of relative concentrations. Relative concentrations of these metals in the samples under study were determined by using energy dispersive X-ray spectrometry and their values were found to be close to the stochiometric relative concentrations in weight of the metals in the precursor aqueous solution. An average size of about 96 Å was estimated for the bi-metallic particles from the full-width at half-maximum value measured for the (2 0 0) diffractometric curve.     

XPS study of the surface chemistry on AZ31 and AZ91 magnesium alloys in dilute NaCl solution

The surface chemistry on AZ31 and AZ91 magnesium alloys was characterized by X-ray photoelectron spectroscopy (XPS) in the corrosion and the passivation zones. In the corrosion zone, the presence of Mg(OH)₂ and MgCO₃ species was found in the outer surface, whereas, in the inner layer, the co-existence of Mg(OH)₂, MgO and MgCO₃ species was observed for both alloys. The presence of Al³⁺ in the surface electrolyte to form Al₂O₃/Al(OH)₃ and the formation of carbonate product provide a better passivation on the surfaces and retard the chloride-induced corrosion on the materials in the passivation zone.     

H等离子体处理对Si中He注入空腔引起的效应

室温下分别采用40,160和1550 keV的He离子注入单晶Si样品到相同的剂量5×10¹⁶cm^-2,部分经He注入过的样品然后再分别接受高密度H等离子体处理.利用透射电子显微镜分析比较了随后800°C高温退火引起的空腔形成.结果表明,附加的H等离子体处理对空腔生长所产生的效应明显地依赖于He离子的能量.对于40 keV He离子注入,空腔的形成和热生长似乎不受H等离子体处理的影响,而对于160 keV He离子注入,附加的等离子体处理则促进了空腔的生长并伴随着空腔分布区域的变窄.对于1550keV He离子注入,H等离子体处理对空腔产生的效应介于40和160 keV注入情况之间.结合H等离子体处理在Si中所引起的缺陷的产生及其热演变过程对实验结果进行了讨论.     

Si离子注入和H等离子体处理对单晶Si中空腔生长的影响研究

室温下首先采用160keVHe离子注入单晶Si样品到剂量5×10¹⁶ions/cm²,部分样品再接受80keVSi离子辐照到较高的剂量5×10¹⁵ions/cm²或接受高密度H等离子体处理.应用透射电镜观测分析了800℃高温退火引起的空腔的形成形貌.结果表明,附加Si离子辐照或H等离子体处理会影响Si中空腔的生长.就Si离子附加辐照而言,由于辐照引入富余的间隙子型缺陷,因此,它会抑制空腔的生长,而高密度H等离子体处理则有助于空腔的生长.定性地讨论了实验结果.     

High pressure studies of viscosity effects on isomerization

Abstract

The viscosity dependence of the isomerization process with comparatively low potential barrier was studied as a model of one-dimensional barrier crossing.

We found that the ground-state isomerization of DODCI fails to fit the Kramers equation. We analyzed this non-Kramers behavior by means of an approach of frequency dependent friction.     

X-ray diffraction studies of heterostructures based on solid solutions Al x Ga1 − x As y P1 − y : Si

The growth of MOCVD-hydride epitaxial heterostructures based on ternary solid solutions Al _x Ga_1?x As heavily doped with phosphorus and silicon has been studied using high-resolution X-ray diffraction and X-ray microanalysis. The prepared epitaxial films are five-component solid solutions (As _x Ga_1?x As _y P_{1 ? y} )_{1 ? z} Si _z .