On the temperature dependence of positron lifetimes in tin and the transition from theβ- to theα-phase

The N₂, O₂, H₂O, and CO₂ molecules that have condensed on the surface of a pyroelectric tourmaline crystal were degassed successively by means of electron bombardment. The temperature dependence of the electrostatic field strength on the specimen surface was observed by electron diffraction; it decreased as the degassing advanced. The tourmaline surface behaved as a gas Chromatographic adsorbent.     

Glasslike thermal conductivity of tourmaline at low temperatures

Thermal conductivity measurements parallel and perpendicular to the c-axis in tourmaline single crystals are reported in the range of 1.7 – 35K. The spontaneous polarization is constrained to the c-axis in tourmaline. The thermal conductivity (K) follows the glasslike K ∝ T^1.9 below 6K in both crystallographic directions, and the magnitude of K is in the upper range found in glasses. It is concluded that the glasslike thermal properties associated with the spontaneous polarization in ferroelectric - type solids occur isotropically throughout the crystal and are not limited to the polarization direction.     

Effect of temperature on the sputtering yield of copper

The effect of temperature on the sputtering yield of copper for low energy argon ion bombardment is investigated. Experimentally, a phase sensitive technique utilizing the spectroscopic emission of sputtered particles is discussed. Analytically, the Langberg model for the sputtering yield is expanded to include the effect of temperature. Atoms of the bombarded surface attain a steady state distribution in the number of their bonds. Changes in either the temperature or the bombardment parameters result in changes in the distribution leading to variations in the sputtering yield. (111) and (110) single crystal and poly crystalline copper surfaces are investigated. Reasonable agreement is obtained between experimental and analytic yield values. The (111) surface shows the largest decrease in yield with an increase in temperature.     

Sputtering during ion implantation into gallium arsenide

The surface erosion caused by ion bombardment of solids and its effect on the number of ions retained in the solid was studied experimentally for a variety of ions implanted into GaAs with various fluences and energies. Experimental methods were interferometry and semi quantitative X-ray analysis by means of an electron microprobe. By an easy-to-use computer calculation the change in the implantation profiles was determined and the number of retained ions were related to the surface shift caused by sputtering. Comparison of this shift with the real erosion found before and after annealing was made. From the results, we conclude that the collapse of the crystal lattice contributes to the sinking of the bombarded surface. Sputtering data necessary to estimate the technical consequences of sputtering, range data of 100 keV Fe ions, and data indicating the sensitivity of X-ray analysis are presented.     

Anomalous heat evolution of deuteron implanted al upon electron bombardment III - try to observe the nuclear d-d reaction

In previous papers, one of the authors (K. K.) has observed the anomalous melting of the surface layer of deuteron implanted Al, containing so-called "tunnel structures", on the electron bombardment in transmission electron microscope. In the present paper, we intended to observe the evidence of the d-d nuclear reaction, expecting neutron emission, associated with the melting phenomenon. However, the result was rather unexpected. The melting phenomenon was certainly observed under the same experimental conditions as before. But, in spite of the melting, neutron emission associated with the nuclear reaction was not observed. And, more unexpectedly, X-ray emission of energy less than roughly 400 v keV was observed when specimens with a bubble structure, which never showed melting, were bombarded with electron beams. Several conceivable mechanisms are discussed which, however, are all not convincing to explain the melting. The melting is attributed to some excess energy generation. The error estimation of the radiation measurements was undertaken.     

2600W偏振耦合高效率半导体激光光源

将两个中心波长为808 nm,输出功率为1500W的半导体激光叠阵,经过快慢轴准直后,利用半波片将其中一个叠阵的偏振方向旋转90°,使用偏振分光平板的耦合功能,将两个偏振方向相互垂直的激光耦合到一个光路.扩束后再通过焦距为100 mm的聚焦镜组聚焦,提高激光器的亮度.在工作电流为75 A时,输出功率达到了2600 W,...     

Bombardment-induced segregation of Cu in Pt-Cu alloy observed using different energy Auger line combinations

Pt_0.19Cu_0.81 alloy scraped in situ was bombarded by energetic (0.2–2 keV) argon ions and the surface compositions under steady-state bombardment were determined with different energy Auger line combinations. It is found that the outermost surface is enriched in Cu, but that its concentration rapidly decreases to a minimum at the second layer then increases slowly to the bulk value. This fact strongly suggests the existence of a bombardment-induced Gibbsian segregation even at room temperature.The project was supported by the National Natural Science Foundation of China     

Electrical and Spectral Characteristics of a Heated Cathode Discharge in Metal Vapors

A new type of discharge in pure metal vapors like copper or titanium is described. A stable discharge is produced between a heated cathode and the anode which has a melted spot on its surface due to the electron bombardment. The spectral characteristics prove that the discharge take place in the vapors of the anode material continuously evaporated from the melted spot on the anode. The discharge has a similar behaviour as the low voltage arc.     

XPS investigation of electron beam effects on a trimethylsilane dosed Si(100) surface

A trimethylsilane covered Si(100) surface at temperature −120°C was bombarded by 1.3 keV electrons for various time intervals. The core level Si2p and C1s electrons were studied after each electron bombardment by use of X-ray photoelectron spectroscopy. The spontaneous dissociation of TMSiH on the Si(100) surface was observed judging from the formation of C---C bonds. The C---C and C---Si bonds increased initially and then saturated after 20 min of electron exposure. The binding energy of C1s in C---C and C---Si bonds and that of Si2p in Si---C bonds showed an opposite behavior under electron irradiation. The former increased and the latter decreased at the beginning of the irradiation and then both increase rate and decrease rate reduced. From the previous results of electron stimulated desorption and temperature programmed desorption, and the variation of electron density distribution around C and Si, it is concluded that the de-hydrogenation in C---H_n and Si---C---H_m bonds was induced and new Si---C and C---Si bonds were formed by electron irradiation on TMSiH covered Si(100) surface.     

Electronic modifications and surface reactivity of an ion bombarded graphite surface

The first steps of structural and electronic modifications of a graphite surface bombarded with argon, hydrogen and deuterium ions were investigated using high resolution electron energy loss spectroscopy (HREELS). The energy and the damping of the low energy plasmon mode of graphite (E//C mode) were studied with respect to the bombardment settings. We show that argon bombardment affects the energy of the plasmon mode, while no similar change is observed after hydrogen (deuterium) bombardments. This can be related to the variation of inter-planar distance between two graphene layers. Moreover, the damping of the plasmon mode can be correlated with the interstitial defect concentration. Concerning the reactivity of the bombarded surfaces, we demonstrate that deuterium bombardment produce a non-deuterated surface. This last is very reactive to a further atomic deuterium exposure, as it is shown by the formation of C-D bondings. The deuterated sites can be removed after thermal annealings between 473 and 783 K. The occurrence of a chemical erosion mechanism accompanying this deuteration is discussed.     

Analysis of polarization switching in ferroelectric crystals in the injection mode

We report on the results of experiments on polarization switching in a ferroelectric TGS crystal during injection of electron beams from a scanning electron microscope under a surface layer. A series of models reflecting the polarization switching dynamics of a ferroelectric crystal under the action of an injected charge is constructed. The implementation of these models is based on the principles of evolution of domain structures taking into account analysis of possible polarization switching mechanisms for ferroelectric samples. A mathematical model developed using these principles demonstrates qualitative similarity of model current pulses and those obtained experimentally in the injection mode.     

CVD金刚石中的氮对等离子体刻蚀的影响

采用非对称磁镜场电子回旋共振等离子体分别对沉积过程中掺氮和未掺氮的化学气相沉积金刚石膜进行了刻蚀研究, 结果表明: 掺氮制备的金刚石膜的刻蚀主要集中在晶棱处, 经过4h刻蚀后其表面粗糙度由刻蚀前的4.761 μm下降至3.701 μm, 刻蚀对金刚石膜的表面粗糙度的影响较小; 而未掺氮制备的金刚石膜的刻蚀表现为晶面的均匀刻蚀, 晶粒坍塌,刻蚀4h后其表面粗糙度由刻蚀前的3.061 μm下降至1.083 μm. 刻蚀导致表面粗糙度显著降低. 上述差别的主要原因在于金刚石膜沉积过程中掺氮导致氮缺陷在金刚石晶棱处富集, 晶棱处电子发射加强, 引导离子向晶棱运动并产生刻蚀, 从而加剧晶棱的刻蚀. 而未掺氮金刚石膜,其缺陷相对较少且分布较均匀 ,刻蚀时整体呈现为 (111) 晶面被均匀刻蚀继而晶粒坍塌的现象. 关键词： 掺氮 金刚石膜 刻蚀 非对称磁镜场     

Characteristic Parameters of the Anode Spot

In most of the works, the anode spot has been shown to be present whenever an electric arc occurs in the wake of an operating contactor, causing a slight contraction of the arc column. The role played by the anode is that of an electron collector, and it has now been acknowledged that the metal surface subjected to electron bombardment is unique with a circular shape. Starting from these hypotheses and using the laws of conservation at the level of the anode spot area, a theoretical model was set up enabling the following parameters to be stated for currents of average intensity (< 2000 A). ra Spot radius. Ta Mean temperature. Ga Erosion speed. Pa Mean pressure. Jea? Current total density. Jea Density of the emitted electron current. The system consisted of a set of six nonlinear equations; however, a numerical solution enabled the values of the six parameters to be stated for a given arc current I. Concerning copper or silver contacts, the results reported will be compared to experimental and theoretical works from other authors. The model proved valid through our own experiments, which showed the evolution of a metal surface subjected to an anode spot. In particular, mention will be made of the redeposition effect which enables the contactors to perform several million operations.     

Ripening of subsurface amorphous C clusters formed by low energy He ion bombardment of graphite

Surfaces of highly oriented pyrolytic graphite (HOPG) were bombarded with 100 eV and 500 eV He ions at ion doses of a few 10¹⁵ cm² and temperatures ranging from 300 K to 800 K. AFM images were recorded to investigate the topography of the surfaces after ion bombardment. Supplementary electron energy loss (EEL) and thermal desorption (TD) spectra were measured to determine the C sp² fraction of the bombarded surfaces and the amount of trapped He. The temperature at which He ion bombardment was performed had a drastic effect on the surface structure and topography of the targets on the angstrom-scale and micrometer-scale as well. At 300 K, limited defect atom transport revealed an amorphous but relatively flat HOPG surface. Bombardment at 400 K leads to a granular structure of small protrusions in micrometer-scale AFM images, however, without crystalline order on the surface. The protrusions are due to the formation of subsurface clusters of carbon formed by atoms displaced by ion irradiation. Towards higher temperatures during bombardment the clusters agglomerate and cause the surface layers to bend upwards in dome-like shapes. Simultaneously, the microscopic order of the graphite lattice recovers. At 800 K large areas of the top layer retain their order during bombardment, however, a small number of domes indicate that there still exist some subsurface C clusters. The cluster–cluster distance deduced from the dome distribution indicates that the clusters grow through a ripening process. Annealing of graphite at high temperatures subsequent to ion bombardment at low temperatures is much less effective for recovering the surface crystallinity than ion bombardment at high temperature.     

The influence of argon ion bombardment on the electrical and optical properties of clean silicon surfaces

The effect of low energy noble gas ion bombardment on the electrical and optical properties of Si(211) surfaces has been investigated by surface conductivity and field effect measurements, ellipsometry and AES. With this combination of techniques, information is obtained concerning the electrical properties, the chemical composition and the damage of the surface layer. Upon ion bombardment in the energy range of 500–2000 eV, ellipsometry shows the formation of a damaged surface layer with optical properties close to those of an evaporated amorphous silicon film. In order to measure the conductivity changes as sensitive as possible, nearly intrinsic silicon crystals were used. For the clean, 5200 Ω cm Si(211) surface, bombarded only with a mass-analyzed argon ion beam, a small increase in conductivity is found to occur after a small ion dose (saturation after 5 × 10¹⁴ ions cm^?2 while after 5 × 10¹³ ions cm^?2 already half of the increase has occurred). The effect was found to be independent of ion energy between 500 and 2000 eV. As the field effect signal did not change after this treatment, it is concluded that the surface state density in the neighbourhood of the Fermi level shows a slight decrease.     

Electron irradiation effect on the surface composition of Ar+ ion bombarded Si-nitride and Si-oxinitride

Auger electron spectroscopy (AES) and electron energy loss spectroscopy (ELS) have been used to study the surface composition of the Si-nitride and Si-oxinitride prepared by low pressure chemical vapor deposition. Ion bombardment has been shown to result in appearance of the “free” silicon on the surface. Electron irradiation of the samples preliminary bombarded by Ar⁺ ions has led to disappearance of the “free” silicon. This process is assumed to be connected with electron stimulated desorption of the “free” silicon.     

Auger electron spectroscopy investigation of sputter induced altered layers in SiC by low energy sputter depth profiling and factor analysis

The thickness of the altered layer created by ion bombardment of the 6H–SiC single crystal was determined by means of Auger electron spectroscopy (AES) depth profiling in conjunction with factor analysis. After pre-bombardment of the surface by argon ions with energies 1, 2 and 4 keV until the steady state, the depth profiles of the induced altered layers were recorded by sputtering with low energy argon ions of 300 eV. Since the position and shape of the carbon Auger peak depend on the perfection of the crystalline structure, they were used for depth profile evaluation by factor analysis. In this way the depth profiles of the damaged surface region could be estimated in dependence on the ion energy. As a result, the thickness of the altered layer of SiC bombarded with 1, 2 and 4 keV Ar ions using an incident angle of 80° as well as the corresponding argon implantation profile could be measured.     

The processes occurring in the surface region of CdS single crystals under electron bombardment,photoexcitation, and gas adsorption and their role in the 80 °K-exciton photoluminescence

Investigations have been carried out in the effect of 3–5 keV electron irradiation, intense photoexcitation, and gas adsorption on photoluminescent spectra of CdS single crystal platelets. CdS platelets subjected to electron bombardment were found to be very active for gas adsorption. The bound exciton emission is influenced by oxygen. A detailed study of the effect of the electron bombardment on the photoluminescence spectra is presented. The results indicate that correlation can be made between the behaviour of the electron bombardment-induced bound exciton emission and the electron processes occurring in the surface region of CdS single crystals. The changes in the photoluminescent spectra caused by the electron bombardment followed by the room temperature photoexcitation, have been interpreted in terms of surface photochemical effects.     

Investigation of surface reactions by the static method of secondary ion mass spectrometry: V. The oxidation of titanium,nickel, and copper in the monolayer range

By means of the static method of secondary ion mass spectrometry the oxidation of a polycrystalline titanium, nickel, and copper surface cleaned by ion bombardment, was investigated in the oxygen dose range up to 1200 L at room temperature. On titanium and nickel two different oxide phases were found, one covering the other. The thickness of the oxide layer on copper did not exceed one monolayer.     

Radiation-assisted formation of microprobes for scanning tunnel microscopes

The formation of tipped tungsten microprobes by ion bombardment in high electric fields with subsequent low-temperature field evaporation is reported. During irradiation, the current density was shown to rise nonmonotonically because of heavy particles present in the bombarding beam due to emitter erosion. It was found that the initially hemispheric working part of the probes turns into the axially symmetric complex-shaped surface. A correlation of these effects with inert gas ionization and tungsten sputtering under the action of super-high-density electron beams is discussed. The atomically smooth microprobes obtained by ion bombardment and field evaporation offer high stability and an atomic-level resolution.