摘要:

The problem of spatial distribution of the temperature rise due to a cw laser beam focused on the surface of an absorbing material is reexamined. The effect of temperature dependence of the absorption and reflection coefficients is incorporated in the calculations in a self‐consistent way. A Green’s function has been developed for the heat diffusion equation in the axially symmetric case and a general steady‐state solution is obtained for an arbitrary source function. Compared with previous results, our calculations predict melting at lower laser power densities and changes in the spatial temperature distribution. In the limit of large absorption constants these differences are small. However, they become increasingly significant as the absorption constant is decreased.

ISSN:0021-8979    

DOI:10.1063/1.335245

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The energy dissipation per cycle due to the harmonic rigid motion of geometric kinks (built‐in) in the atmosphere of light interstitials which are hopping between tetrahedral sites is investigated analytically as well as numerically in terms of discrete Fourierkspace plus Laplace transformation technique. In the linear response case a discrete Debye‐type relaxation spectrum with six distinct branches is found to represent the anelastic behavior of the system uniquely (the nearest neighbor jumps only) and exactly. It is shown by extensive computer modeling experiments that the induced and dislocation embedded kink‐enhanced Snoek peak is composed of six subpeaks, one acoustic and five optical in character. The acoustic part and the optical modes, especially the upper band which is composed of optical modes 6 and 5, are strongly and selectively associated with the isotropic (Cottrell Atmosphere) and the pure shear part (Snoek Cloud) of the elastic dipole tensor of the tetrahedral interstitials, respectively. An extremely accurate and concise analytical expression is deduced which shows that the decoupling procedure of Snoek and Cottrell atmospheres is a reliable approximation.

ISSN:0021-8979    

DOI:10.1063/1.335246

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Electron bombardment of thick pure SiO2induces the buildup of a negative charge which can be observed through a ‘‘mirror’’ effect in a conventional Auger scanning microscope. A mechanism for the creation of this charge is proposed in terms of trapping of an electron in defects due to the irradiating beam. The influence of temperature is studied on amorphous and monocrystalline SiO2. The temperature dependence of the existence of high negative charge shows around 270 °C an anomalous effect which depends on the irradiation time. The role of electronic excitation to produce defects in silica is discussed.

ISSN:0021-8979    

DOI:10.1063/1.335247

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

It is found by deep level transient spectroscopy (DLTS) that the oxygen thermal donor formation is suppressed in Czochralski silicon doped with donor impurities more than 1×1016cm−3. The result is explained by a new model considering electron‐hole equilibrium. The dopant concentration dependence of the thermal donor formation is analyzed, based on the model, and it is concluded that the thermal donor is a doubly charged donor.

ISSN:0021-8979    

DOI:10.1063/1.335248

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Acceptor (B, Al, Ga, and In) density versus time curves during avalanche electron injection (AEI) and constant‐temperature thermal annealing experiments obtained from metal‐oxide‐silicon capacitors (MOSCs) show two distinguishable phases. The time dependence of the acceptor density during AEI shows an initial delay due to electron‐impact release of hydrogen trapped in the gate conductor and oxide layers and a long‐time decay due to the thermal capture and electron‐impact emission of the atomic hydrogen at the group‐III acceptor centers in the silicon surface layer. Thermal anneal of hydrogenated acceptor begins at 50 °C for boron and 100 °C for Al, Ga, and In. The initial phase during thermal annealing of AEIed MOSCs follows a first order kinetics at higher annealing temperatures, reaching a steady‐state acceptor density before the second phase begins. The long‐time anneal follows strictly a second‐order kinetics which is rate limited by the recombination of two hydrogen atoms to form a molecule. Incomplete anneal is observed at higher temperatures when the dissociation rate of the hydrogen molecule becomes comparable with the recombination rate of two hydrogen atoms. Analytical solutions are obtained which account for all the details of the observed hydrogenation and annealing curves. These solutions are used to evaluate the thermal capture and emission rates and electron‐impact emission rates of hydrogen or proton at the group‐III impurity centers and the bimolecular generation and recombination rates of hydrogen. A new concept of hydrogen or proton traps in analogy to the electronic hole or electron traps is introduced to analyze the kinetics and account for the observed chemical trends between thermal capture and emission rates, thermal activation energy and bond strength. Chemical trends are noted which are consistent with the trapped proton activation energy and hydrogen bond strength trend, B<Al<Ga<In.

ISSN:0021-8979    

DOI:10.1063/1.335249

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The influence of low‐energy (E∼5 eV per proton) ionizing radiation on predamaged, amorphous SiO2has been studied through the electron spin resonance of oxygen vacancy centers (E’1). It is demonstrated that the observed line shapes can be explained in terms of dipolar broadening. By independent methods, line‐shape fitting, and numerical integration, we extract the defect density as a function of low‐energy irradiation dose and observe significant annealing for doses in excess of 10 J/cm2accumulated. For medium‐energy proton irradiations, contradictory results of line fitting and integration suggest the overall number of defects increases during proton irradiation but the mean defect density decreases (i.e., the defect‐defect spacing increases). The fractional increase in defect numbers is much smaller than that found by others using 1‐MeV electron irradiation.

ISSN:0021-8979    

DOI:10.1063/1.335250

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

160‐nm polycrystalline silicon films were implanted at room temperature with 100‐keV silicon ions and subsequently annealed. The final grain size was found to increase with implant dose. A model is presented here to account for the dose dependence of the grain size. Three mechanisms were presumed to account for the final grain size: statistical variations of area coverage by the implanted ions, ion channeling, and spontaneous nucleation. Model parameters were successfully fit to the experimental data.

ISSN:0021-8979    

DOI:10.1063/1.335251

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The concentrations ofE’centers (ESR‐active oxygen vacancies) produced by 30–160 keV electron irradiation have been measured in thermal SiO2films at doses far exceeding any previously reported. The dependences of these concentrations on electron energy and fluence were measured in both steam‐grown and dry oxides. Results indicated that ionization rather than atomic displacement is the predominant formation mechanism. Significant differences in dose dependence were found between oxide types, reflecting the role of hydrogen in damage annealing.

ISSN:0021-8979    

DOI:10.1063/1.335252

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The amphoteric nature of silicon in gallium arsenide is used to develop diffusion and electrical compensation mechanisms. The diffusion mechanism is based on the formation and diffusion of nearest‐neighbor donor‐acceptor pairs. General solutions are presented that predict abrupt diffusion fronts for a wide range of pairing conditions. Experiments support the application of this mechanism to Si diffusion in GaAs at high concentrations. A compensation mechanism for amphoteric dopants is developed as well. The compensation process is driven primarily by the free‐electron concentration. Nearly complete compensation is predicted for large dopant concentrations.

ISSN:0021-8979    

DOI:10.1063/1.335253

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A simple atomic structure model was proposed for Ga1−xInxAs solid solution. Distortion energy caused by the differences in Ga‐As and In‐As bond lengths was calculated using the valence‐force‐field approach. Calculated bond lengths for Ga1−xInxAs agree well with the extended x‐ray absorption fine structure data. The calculated mixing enthalpy which corresponds to the excess energy caused by distortions agree with that from phase diagram.

ISSN:0021-8979    

DOI:10.1063/1.335254

出版商:AIP    

年代:1985

数据来源: AIP