摘要:

We present new evidence that two electron traps observed in polycrystalline zinc oxide can be associated with complex intrinsic defects. One deep level, E1, can be assigned to an oxygen vacancy. The second deep level, E2, could consist of a cluster‐type defect associated with oxygen vacancies. The two traps were characterized using deep‐level transient spectroscopy. The energies of these traps are 0.15 and 0.24 eV, the capture cross sections are 4×10−18and 1×10−17cm2, and the emission rates at 300 K are 2.0×106and 1.3×105Hz, respectively. The relative concentrations of these traps varied uniformly as a function of the cooling rate of the zinc oxide from a sintering temperature of 1300 °C. The concentration of E1 decreased, while the concentration of E2 increased, with decreasing cooling rate.

ISSN:0021-8979    

DOI:10.1063/1.345114

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Iron is one of the most important impurities in silicon integrated‐circuit technology. We present a fast (5 min), essentially preparation‐free large‐area (25 cm2) technique to determine the Fe concentration in boron‐doped silicon with a sensitivity of 2–5×1011cm−3. The principle of the method is based on the fact that interstitially dissolved Fe undergoes a reversible pairing reaction with boron and that the minority‐carrier diffusion length—as measured by the surface photovoltage method—is modified by this reaction. The method has been calibrated by deep‐level transient spectroscopy and is also suitable to measure a surface Fe contamination in combination with a rapid thermal annealing diffusion step.

ISSN:0021-8979    

DOI:10.1063/1.345063

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A series ofa‐Si:H films has been prepared by rf sputtering in a H2‐Ar gas mixture. To obtain films with different hydrogen content the hydrogen portion of the gas mixture was changed from 0% to 20%. The shear modulus &mgr; was then measured by the frequency of the surface phonon (Rayleigh wave). The stiffnessSand the ultramicrohardnessHwere measured by using a nanoindenter. From the shear modulus &mgr; and the stiffnessS, the Young’s modulusEand Poisson’s ratio &ngr; were calculated. The intrinsic mechanical stress was measured by the bending‐beam method. With increasing hydrogen content of the films, the decrease of Young’s modulus, microhardness, and internal stress are observed.

ISSN:0021-8979    

DOI:10.1063/1.345064

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Dispersion of elastic waves in a bonded plate has been analyzed using the exact solution as well as by two approximate models: a spring model that neglects the inertia effects and a density model that does not account for the finite stiffness of the bond layer. It is shown that the two model predictions agree with the exact solution in two overlapped regions of the density and stiffness ratios. However, they fail to predict the actual behavior in certain regions of the parameter domain.

ISSN:0021-8979    

DOI:10.1063/1.345065

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The solution of the problem of diffraction of obliquely incident longitudinal waves by two equal, parallel, and coplanar Griffith cracks embedded in an infinite, isotropic, and homogeneous elastic medium is solved by a simple integral equation technique. Approximate expressions for the stress intensity factors, far‐field amplitudes, and scattering cross section are obtained when the wavelengths are large compared to the distance between the outer edges of the two cracks. By taking appropriate limits in these expressions, we derive some interesting and new results. The values of stress intensity factors and the scattering cross section are computed and various graphs of these physical quantities of interest are plotted.

ISSN:0021-8979    

DOI:10.1063/1.345066

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Silicon layers have been grown on Si substrates from Ga‐rich solutions by liquid‐phase epitaxy at temperatures between 615 and 1220 K. The diffusion coefficient of Si in liquid Ga is estimated from layer thickness data to beDGaSi=0.0235 exp(−4016 K/T) cm2/s. The incorporation of Ga in the Si layers was investigated by means of neutron‐irradiation, double‐crystal x‐ray rocking curve, Auger recombination, infrared reflection, Rutherford backscattering, and Hall effect experiments. Below 850 K the normal retrograde solid solubility of Ga in Si changes to an anomalous nonretrograde solubility. The doping level increases fromp=5×1018cm−3to 5×1020cm−3at 615 K. The concentrations of net carriers, ionized Ga impurities, and total Ga atoms are identical over the entire temperature range, showing that Ga atoms are incorporated on lattice sites. Imperfections such as dislocations, stacking faults, or precipitates are not responsible for such high levels. The occurrence of Si vacancies or microsegregation due to lateral growth are possible driving forces causing this anomalous behavior. Excess free‐energy contributions resulting from internal stress produced by lattice mismatch may also provide a mechanism for producing this effect.

ISSN:0021-8979    

DOI:10.1063/1.345067

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Interfacial reactions between iridium and gallium arsenide in both the thin‐film and bulk forms have been investigated in the temperature range 400 to 1000 °C using transmission electron microscopy, energy dispersive x‐ray analysis, and electron probe microanalysis. The diffusion path for Ir/GaAs has been determined to be Ir/IrGa/IrAs2/GaAs and is consistent with the phase diagram between the initial stages of reaction (thin‐film) and long‐term annealing (bulk). In the thin film case where the Ir supply is limited, the final configuration is Ir3Ga5/ IrAs2/GaAs. The diffusion path and reaction morphology has been rationalized using the phase diagram, kinetic observations, and growth mechanisms observed during the reactions.

ISSN:0021-8979    

DOI:10.1063/1.345068

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The stress generated during thermal cycling of electron‐beam‐evaporated Cr‐Co and Ti‐Co films on quartz substrates was measured by means of the cantilever bending‐beam technique between 20 and 550 °C. The thickness ratio was selected to correspond to an atom ratio of [Co]/[Cr] and [Co]/[Ti]>3. In the unreacted films, the residual stress after cycling is tensile and comparable with that in pure Co. In Co‐Cr films there is only a slight increase in stress after complete reaction, whereas a marked increase in tensile stress is observed in Co‐Ti films. Phase formation and reaction kinetics were investigated by Rutherford backscattering and x‐ray diffraction. The dominant phases in Co‐Cr are solid solutions of Cr in Co and Co in Cr with the same structure as the original films. In Co‐Ti the main reaction product is the intermetallic compound Co3Ti with the Cu3Au structure. The formation of Co3Ti, which is accompanied by volume shrinkage, is diffusion controlled. The high activation energy of 2.4±0.2 eV suggests volume diffusion of Co through the growing phase as a rate limiting process.

ISSN:0021-8979    

DOI:10.1063/1.345069

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Experiments are described determining the critical parameters for vacancy‐ and impurity‐induced layer disordering of AlxGa1−xAs‐GaAs quantum‐well heterostructure (QWH) crystals that utilize SiO2and Si3N4diffusion source layers. The SiO2‐ or Si3N4‐capped QWH crystal surface reaches equilibrium with the external annealing ambient by diffusion of Ga and As through the encapsulant layer, thus determining the crystal‐surface deviation from stoichiometry and the column III vacancy concentration for layer disordering. By proper design of the QWH crystal, encapsulant layer thickness, and annealing ambient, the SiO2(Si3N4) can be employed as a column III vacancy source (or mask) or as a Si and O (or N) diffusion source to effect impurity‐induced layer disordering.

ISSN:0021-8979    

DOI:10.1063/1.345070

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Molecular‐beam epitaxy has been successfully used to grow InAsxSb1−xon InP substrates with good electrical characteristics. The samples are allntype with electron concentrations varying in the range (3–9)×1015cm−3. The mobilities are high (70 000 and 110 000 cm2/V s at 300 and 77 K, respectively) in InSb and the alloys. More importantly, the mobilities remain high at the low temperatures in the alloys also, without any type conversion. The mobility data have been analyzed taking into account the appropriate scattering mechanisms. The alloy scattering potential in InAs0.24Sb0.76is estimated to be 0.3 V.

ISSN:0021-8979    

DOI:10.1063/1.345071

出版商:AIP    

年代:1990

数据来源: AIP