摘要:

The thermoelastic equations are solved for laser heating of a semi‐infinite elastic medium by a focused TEM00Gaussian beam. Single integral expressions are derived for stresses and strains, which are analytically evaluated on axis at the surface and far from the laser‐heated region (for a laser spot size≫absorption depth), and numerically evaluated for the example of laser heating of a silicon substrate. This analysis is extended to the case of laser heating of thin films on substrates. Use of these stress and strain profiles suggests that dislocations may form at the surface during high‐temperature laser processing of silicon at scan speeds typically used in direct laser writing. Also the elastic strains induced during laser heating shift phonon frequencies from their thermal equilibrium values, thereby complicating the use of Raman scattering as an optical probe of temperature. This is shown to be particularly significant for laser heating of silicon thin films on fused silica substrates and not very important for laser processing of silicon substrates or silicon thin films on sapphire.

ISSN:0021-8979    

DOI:10.1063/1.342086

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Grain boundary diffusivities of a110Ag radioactive tracer have been measured in polycrystalline Pb specimens over a temperature range of 57–118 °C. Diffusivity parameter values are expressed by the Arrhenius relation:P(cm3 s−1)=Dgb&dgr;&agr;=1.58×10−4×exp(−41120 J mol−1/RT). These values are five orders of magnitude higher than those relative to self‐grain boundary (gb) diffusivity of lead. Thus, the difference between silver and lead grain boundary mass transport is almost the same as that measured for bulk diffusion. The possible explanations for such a similarity are discussed in relation with the particular bulk diffusion mechanism of silver and a possible high grain boundary segregation of this solute.

ISSN:0021-8979    

DOI:10.1063/1.342513

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

We report detailed measurements of gold concentration profiles in ⟨100⟩,p‐type silicon. The gold has been introduced by ion implantation and diffused in the temperature range 1073–1473 K and for times ranging from 60 s to 100 h. The resistivity profiles have been converted into gold concentration profiles by using the recently measured value of the entropy factor for the ionization of the gold donor level. The measured profiles and their time dependence can be accounted for by the kick‐out diffusion mechanism. The activation energies for the effective diffusion coefficient and for the gold substitutional concentration are 1.7±0.1 and 1.6±0.1 eV, respectively. The resulting flux of silicon self‐interstitials is thus described by an activation energy of 3.3±0.1 eV.

ISSN:0021-8979    

DOI:10.1063/1.342087

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

We report the epitaxial growth of silicon on a CaF2/Si(111) heteroepitaxial structure. The results show that contrary to previous reports, the room‐temperature predeposition of a very thin layer of silicon does not significantly affect the problem of calcium migration to the top surface of the silicon film, although it appears to improve the surface morphology of the film. Planar and cross‐sectional transmission electron microscope and x‐ray diffraction studies have shown that the silicon film, although single crystalline, is highly defective, the main defects being twins on both the inclined {1¯11} planes and the parallel (111) planes.

ISSN:0021-8979    

DOI:10.1063/1.342088

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Low to moderately boron‐doped silicon crystals were irradiated at room temperature with a 2.0‐MeV electron beam and studied by means of deep‐level transient spectroscopy. New dominant hole trapsH(0.12) andH(0.07) located, respectively, at 0.12 and 0.07 eV above the valence band, and an electron trapE(0.59) located at 0.59 eV below the conduction band are reported. The statesH(0.12), produced directly after irradiation, andH(0.07), formed following 400 °C annealing, are observed in samples of low boron contents (∼1014cm−3). The stateE(0.59), on the other hand, is observed after 400 °C annealing in the moderately boron‐doped samples (∼1015cm−3). Based on the thermal stability and energy position of these states tentative defect identifications are proposed by correlation with published data. Other previously reported hole traps are observed at 0.22 and 0.34 eV above the valence band and are ascribed to the divacancyV2(0/+) and the carbon interstitial‐carbon substitutional pair, respectively.

ISSN:0021-8979    

DOI:10.1063/1.342089

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Deep levels in iron‐diffused heavily boron‐doped silicon are investigated by means of deep‐level transient spectroscopy (DLTS). For interstitial iron Feia donor state is observed at 0.39 eV above the top of the valence bandEv. It is proposed that Feiexhibits charge‐dependent annealing characteristics, and in its neutral charge state Feiis mobile at temperatures as low as ≊280–230 K. Three other Fe‐related donor states are observed atEv+0.53 eV,Ev+0.60 eV, and ≊Ev+0.63 eV. The latter two states, not reported in any previous DLTS study, are produced in comparable concentrations to that of Feiupon annealing at 100 °C, whereas the former state present directly after quenching is suggested to result from a complex defect containing Fei. It is also argued that the level observed in this study atEv+0.60 eV is the same as the one reported earlier at 0.55 eV below the bottom of the conduction band, but that it corresponds to a donor state of an Fe‐related defect, in contrast to previous suggestions of it being an acceptor state. The annealing behavior of the defect states observed is studied up to 300 °C, and possible interactions involving Feiare discussed.

ISSN:0021-8979    

DOI:10.1063/1.342090

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The effects of the two sampling gate positions, and their widths and the integrator response times on the position, height, and shape of the peaks obtained in a double‐channel gated‐integrator‐based deep‐level transient spectroscopy (DLTS) system are evaluated. The best compromise between the sensitivity and the resolution of the DLTS system is shown to be obtained when the ratio of the two sampling gate positions is about 20. An integrator response time of about 100 ms is shown to be suitable for practical values of emission time constants and heating rates generally used.

ISSN:0021-8979    

DOI:10.1063/1.342091

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

We have found that undoped semi‐insulating GaAs substrates convert from semi‐insulating to strongly conductingp‐type behavior following high‐temperature annealing (830 and 885 °C) for long periods of time (22–60 h). Remarkably similar results have been obtained for both liquid‐encapsulated Czochralski and horizontal Bridgman undoped semi‐insulating GaAs synthesized by various manufacturers. Hole concentrations measured at room temperature are aboutp=9.1×1015and 3.6×1016cm−3after 830 and 885 °C anneals, andpis uniform throughout the 380 to 510 &mgr;m substrate thickness for 885 °C anneals. Hall‐effect measurements of carrier freeze‐out indicate that residual carbon acceptors are the dominant shallow‐acceptor species. Conversion toptype appears to arise from out‐diffusion of EL2 deep donors and from formation of an additional acceptor‐type native defect which also results from arsenic out‐diffusion during annealing.

ISSN:0021-8979    

DOI:10.1063/1.342092

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The energy position of an iodine‐related donor has been tracked through the alloyed system ZnSxSe1−x, where 0.60<x<1.00. Both optical and thermal energies have been measured with junction space‐charge techniques. The results suggest that the optical threshold energies and lattice‐relaxation effects are almost independent ofx, although the activation energy of the thermal emission rate increases considerably with increasingx. Detailed measurements of the temperature dependence of the capture cross section for electrons show that the enthalpy of the iodine‐related center is fairly constant for higher values ofx.

ISSN:0021-8979    

DOI:10.1063/1.342093

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Valence shell electronic excitations in silicon, and its carbide, nitride, and oxide are studied using electron energy loss microspectroscopy in a transmission electron microscope, at 1‐eV resolution with a 100‐keV electron beam. This so‐called ‘‘low‐loss’’ region of the spectrum is normalized to scattering cross section per valence electron for each compound, and a large, sequential, variation in the cross section across the series of compounds is reported. The low‐loss cross section is calculated using the Born approximation by including single‐electron transitions in the target. Both band‐to‐band and band‐to‐continuum transitions are included, by using extended Hu¨ckel band calculations to obtain the valence shell crystal states, using the electron gas model for the ionization states, and using the random phase approximation to obtain differential cross sections. The calculations yield semiquantitative results, and allow for a chemical interpretation of the experimental results. The relation of the present model to that for plasmon excitation is also briefly discussed.

ISSN:0021-8979    

DOI:10.1063/1.342094

出版商:AIP    

年代:1988

数据来源: AIP