摘要:

A report on the adequacy of the collinear mirage technique for thermal diffusivity measurements on bulk homogeneous solids is presented. A 3D theoretical model for collinear deflection has been developed from which two simple linear relations between measurable parameters and the thermal diffusivity have been obtained. Two methods, the so‐called zero‐crossing and phase methods, are discussed in detail. The second one seems to be a promising tool for thermal diffusivity determination. It has been validated by means of experimental measurements on a set of samples with known thermal diffusivities. The technique is restricted to semitransparent solids but is also valid for materials with either high or low thermal diffusivities, being specially useful for this last group.

ISSN:0021-8979    

DOI:10.1063/1.354854

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The charge transfer collision cross section of He+ions in a collisional helium plasma has been determined based on the ion energy distribution at the target during the plasma immersion ion implantation (PIII) process. The ion energy distribution is obtained by inferring data from a secondary‐ion mass spectroscopy measurement and a simple collisional theory. The value of the charge transfer cross section in the collisional plasma was found to be higher than previously published values. The cross‐section value determined by the PIII technique was used in a plasma simulation and was found to agree with our experimental observations.

ISSN:0021-8979    

DOI:10.1063/1.354855

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A one‐dimensional longitudinal model of a XeCl discharge including the cathode region, the plasma, and the external circuit has been used for conditions close to experiments for 50–100 ns laser pulse durations and electron power deposition in the MW/cm3range in a 300 cm3chamber. This model provides the space and time variations of the electric field, electron and positive‐ion densities in the cathode region, as well as the time variations of the charged‐particle densities and excited species concentrations in the plasma obtained with a simplified kinetic model. Results show that under normal conditions of operation the cathode electric field can reach values as high as several 106V/cm. The influence of photoemission and secondary emission due to ion impact on the cathode is discussed. A transition from capacitive to resistive behavior of the sheath is seen to occur rapidly due to the multiplication of cathode‐emitted electrons in the large sheath electric field, leading to a fast increase in the ion conduction current in this region. The possible mechanisms of streamer formation in the sheath are also discussed. Results are presented for different values of the secondary electron emission coefficient due to ion impact from the cathode and it is shown that under conditions of low secondary emission (on the order of 10−2or less), the electrical and chemical behavior of the plasma can be strongly affected by the presence of the sheath. Finally, the possibility of discharge instabilities related to the sheath evolution is briefly discussed on the basis of the numerical results.

ISSN:0021-8979    

DOI:10.1063/1.354856

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Experimental observations of the energy‐dependent electron‐beam penetration in type II‐A natural diamond are reported. The experimental data are compared with results obtained from numerical Monte Carlo simulations, and the results are in very good agreement. The results also reveal that a threshold energy of about 125 keV is necessary for complete penetration for a 35 &mgr;m sample. It is found that over the 30–180 keV range, the energy dependence of the penetration depth and total path length exhibits a power‐law relation. Monte Carlo simulations have also been performed to investigate the excess carrier‐generation profiles within diamond for a set of incidente‐beam energy distributions. The simulation results demonstrate the feasibility of tailoring the internal source function, and hence influencing the diffusion currents, the internal electric fields, and charge injection through the contacts.

ISSN:0021-8979    

DOI:10.1063/1.354829

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Water vapor added to NF3plasma during reactive ion etching controls the ratio of the etch rates of SiO2and Si. Selectivity rises from a value of 0.14 at water‐free 100% NF3to 1.99 for an initial gas composition of 35% H2O‐65% NF3. The results of mass and energy analysis of the plasma yield a basis for discussing the mechanisms which effect the selectivity. The NF3/H2O plasma removes native oxides from Si surfaces.

ISSN:0021-8979    

DOI:10.1063/1.354830

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A Monte Carlo simulation is presented for the transport of mercury 254 nm radiation in the cylindrical positive column of an argon‐mercury fluorescent lamp. Of particular interest are factors influencing the fractionfof photons which, once initially created by electron impact excitation in the volume of the lamp, actually escape to the outer wall of the lamp rather than being lost to nonresonant quenching. Increases infof up to ≊6%, reported earlier from a similar model [Andersonetal., Phys. Rev. A31, 2968 (1985)], are confirmed for artificial increases in the abundance of the196Hg isotope to ≊10%. Other manipulations of the isotopic mercury content are investigated here, but none increasefby more than a few percent. Externally applied axial magnetic fields up to 0.15 T are found to increasefby up to 15%.

ISSN:0021-8979    

DOI:10.1063/1.354831

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A silicon wafer was implanted by a high dose of cobalt ions. Afterwards it was annealedinsituwhile grazing incidence x‐ray diffraction measurements in a temperature range up to 690 °C were carried out. The formation of cobalt disilicide (CoSi2) precipitates starts during implantation. The annealing dependence of the precipitate growth, of strain relaxation, and of improvements of the silicide crystallinity was determined. We got an activation energy of (0.47±0.08) eV for the observed annealing process. The result is a buried cobalt disilicide layer with very rough interfaces. The film quality can be improved by a subsequent annealing at about 1000 °C.

ISSN:0021-8979    

DOI:10.1063/1.354832

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Thermally stimulated depolarization current (TSDC), thermal sampling (TS) TSDC, and dielectric spectra of poly(p‐phenylene sulfide) (PPS) were measured in the vicinity of the glass transition temperatureTg. The global TSDC spectra of amorphous PPS with varying the poling temperature revealed the presence of two TSDC peaks. Only a very intense peak associated with the &agr; relaxation (the glass transition) was observed at 367 K in the global TSDC spectra poled at above 360 K, while an additional peak was observed at around 330 K in those spectra poled at below 355 K. This additional peak observed at belowTgwas considered to be originated from the secondary sub‐Tgrelaxation. Both the sub‐Tgand the &agr; relaxations were analyzed from elementary TSDC spectra obtained by the TS technique. It was found that the temperature dependence of the relaxation times in both relaxations was ruled by the same compensation law. The physical meaning of the compensation temperature is discussed in relation to the thermal‐expansion coefficient. Moreover, the dielectric constant &egr;’and dielectric loss factor &egr;‘of amorphous PPS are calculated using the relaxation parameters derived from the TS‐TSDC analysis. Numerical results of dielectric data are represented by three‐dimensional and/or two‐dimensional spectra and are compared with the available experimental data. The simulated dielectric spectra forecast that the sub‐Tgrelaxation should appear as a peak or shoulder of &egr;‘at lower‐temperature and ultra‐low‐frequency regions in the ac measurements.

ISSN:0021-8979    

DOI:10.1063/1.354833

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A new type of sensitive electro‐optic effect in a nematic liquid‐crystal (4‐cyano‐4’‐5‐alkyl‐bipheneyl) cell with polymer thin films is reported. Optical switching in a transmitted intensity of light passing through a cell is experimentally observed by dual low‐frequency modulation method using a triangular wave application. Dielectric relaxation effects in the thin polymer layer as part of the cell serve to reduce the effective voltage acting on the liquid‐crystal layer for lower frequencies but not for higher frequencies. The mean effective applied voltage to a liquid‐crystal layer is efficiently controlled by changing only the frequency.  

ISSN:0021-8979    

DOI:10.1063/1.354808

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The electrical activation characteristics of Si+and Be+ions implanted into InGaAsP (&lgr;=1.3 &mgr;m) grown lattice matched to InP by metalorganic molecular beam epitaxy were studied as a function of ion dose (5×1012–5×1014cm−2), annealing time (3–60 s) and annealing temperature (575–750 °C). Maximum doping concentrations of ∼2×1019cm−3were obtained for both Si+and Be+, with activation energies for electrical activation of 0.58 and 0.39 eV, respectively. Multiple energy F+or H+implants can be used to produce high resistance layers for isolation purposes—maximum sheet resistances of ∼8×106&OHgr;/&laplac; or ∼106&OHgr;/&laplac; for initiallyp+orn+InGaAsP, respectively, were obtained for F+implants followed by annealing near 450 °C. Smooth, anisotropic dry etching of the InGaAsP is obtained with electron cyclotron resonance CH4/H2/Ar discharges at low dc biases. The etch rates are the same for bothn+andp+quaternary layers and are independent of the doping level.  

ISSN:0021-8979    

DOI:10.1063/1.354809

出版商:AIP    

年代:1993

数据来源: AIP