摘要:

The diffusion of a fluorinated hydrocarbon into glassy poly(styrene) (PS) was studied by using resonance nuclear reaction analysis. It was found that; (1) the activation energy derived from measured diffusion coefficients is in good agreement with the value calculated from measured induction times, (2) the diffusion coefficient depends on molecular weight of PS, reflecting the dependence of the mobility on the polymer chain matrix, (3) the mathematical foundation of Lasky and Kramer provides a framework to obtain swelling kinetics from the experimental diffusion measurements.

ISSN:0021-8979    

DOI:10.1063/1.351327

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Interactions of point defects with SiO2films play a central role in integrated circuit fabrication processes. In this work, a model is developed for the Si‐SiO2system that considers the segregation of excess silicon between the oxide and the silicon substrate and diffusion and reaction of that excess silicon in SiO2. The model is able to explain a broad range of experimental observations under both oxidizing and nonoxidizing conditions in a consistent manner including: the variation of interstitial supersaturation with oxidation rate in steam and dry O2ambients, oxidation enhanced and retarded diffusion results in ⟨100⟩ and ⟨111⟩ silicon, the large interstitial supersaturation resulting from the nitridation of SiO2, the reduction of SiO2in argon and the corresponding decrease in interstitial concentration, contradictory calculations of effective interstitial diffusivity, and the greatly reduced effective recombination velocities for nitrided oxides relative to capped oxides.

ISSN:0021-8979    

DOI:10.1063/1.351328

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

An extensive investigation on the diffusion and precipitation of Sb implanted in Si has been carried out. The rapid epitaxial regrowth of the amorphous layer produced by the incident ions brings Sb atoms into a substitutional position up to a concentration threshold of about 3.5 × 1020cm−3. This high supersaturation (the solubility of Sb in Si is about 2 × 1019cm−3at 1000 °C) and the low value of the surface free energy facilitate the nucleation of precipitates, which form and grow in concomitance with the diffusion during the annealing. The kinetics of the precipitation has been investigated at 800, 900, and 1000 °C with isothermal treatments ranging between 3 min and 341 h. The experimental data have been compared with the results of a simulation program that takes into account the precipitation phenomena. Good agreement has been obtained for all the investigated experimental conditions both for total and carrier distributions. The model represents a significant improvement of the simulation of Sb diffusion in silicon; in fact, the more commonly used process codes are inadequate to correctly foresee the dopant distribution in supersaturated conditions.

ISSN:0021-8979    

DOI:10.1063/1.351329

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Heavily carbon (C)‐doped GaAs grown by low‐pressure organometallic vapor phase epitaxy using carbon tetrachloride exhibits a lifetime significantly lower than that obtained by zinc doping in previous work and does not exhibit strain relaxation for thicknesses above twice the critical thickness for misfit dislocation formation (hc). GaAs:C+is shown to be thermally unstable to annealing cycles as brief as 600 °C for 4 min. The instability is manifest in conductivity, photoluminescence intensity, and lattice contraction reduction for carbon concentrations above 7×1019cm−3. This reduction is not alleviated by reducing the layer thickness belowhcor adding indium to increasehcabove the layer thickness. This suggests that eitherhcis not an adequate measure of misfit dislocation formation during annealing or misfit dislocation generation is in general not responsible for the thermal instability of GaAs:C+.

ISSN:0021-8979    

DOI:10.1063/1.351330

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The composition of SrF2thin films deposited on carbon plates by sublimation under ultrahigh vacuum has been investigated mainly by Rutherford backscattering (RBS) of &agr; particles as a function of the substrate temperature during the condensation phase and of the thickness of the layers. It is shown that forTS= 270 °C the obtained films are stoichiometric, homogeneous, and quasi‐insensitive to air exposure. The structure of such layers grown on (100)InP single crystals has been deduced from the study of channeling phenomenon. It is demonstrated that the RBS minimum yield &khgr;min, measured on SrF2, decreases with increasing thin‐film thickness, varying from 100 to 400 nm. For a 400‐nm‐thick SrF2thin film at 350 nm from the interface &khgr;min=0.05 showing that the layer is well crystallized and presents the same orientation as the substrate.

ISSN:0021-8979    

DOI:10.1063/1.351331

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A simulation of Cu L&agr; and Cu K&agr; diffractions from W/Si multilayers with a local layer‐thickness deviation at various depths of the multilayers has been presented. The results show that the peak intensity decreases rapidly at first while increasing the depth of the local deviation, and then the peak splits into double peaks. But, afterward, the double peaks coincide again. These changes are affected by the ratios (x) of heavy‐atom layer thickness to total period thickness. The intensities of the double peaks are nearly equal whenxis 0.5, but are quite different whenxis 0.22. The changes due to the local deviation are different from those due to random fluctuations or systematic deviations in periods. An explanation has been carried out by the amplitude‐phase diagrams.  

ISSN:0021-8979    

DOI:10.1063/1.351332

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

An equilibrium model for agglomeration in polycrystalline thin films which considers the energy balance between the grain boundary energy and both surface and substrate interface energies is presented. It predicts that small grain size, low grain boundary energy, and high film surface and interface energies should promote resistance to agglomeration, and shows that the substrate‐film interface can play a significant role in the process. It also predicts a critical grain size limiting formation of a discontinuous island structure. This easily calculable value is significantly smaller than that found in previous modeling. The critical grain size, the importance of the substrate interface, and some of the assumptions are shown to be consistent with transmission microscope observations of TiSi2thin films deposited on Si substrates.

ISSN:0021-8979    

DOI:10.1063/1.351333

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Electron trap generation in thermally grown silicon dioxide (SiO2) during Fowler–Nordheim (FN) stress is investigated by using an aluminium‐gated capacitor structure. The generated electron traps are characterized by the avalanche electron injection technique. The experimental results support the model that electron trapping in oxide follows the first‐order kinetics and may have multiple‐capture cross sections. It is found that both donorlike (positive charge related) and acceptorlike (neutral before capturing electron) traps are generated and they behave differently. The donorlike trap is not stable at or above room temperature and its effective density saturates as the stressing time increases, while the opposite is true for the acceptorlike trap. The electron‐capture cross section of donorlike trap spreads from 10−18to over 10−14cm2, but the capture cross section of the generated acceptorlike trap is limited in the range of (4.5–9)× 10−17cm2. The acceptorlike trap is generated by the interaction between free holes and SiO2and hole trapping leads to donorlike traps. The relation between the generated trap and the as‐grown trap will be discussed. Comparison of the electron traps generated by FN stress with those by irradiation and hot hole injection indicates that the electron trap generation under these different stressing conditions is controlled by the same mechanism. The necessary condition for electron trap generation is the presence of holes in the oxide, rather than a high electrical field.

ISSN:0021-8979    

DOI:10.1063/1.351334

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A theory of steady‐state conduction of injected space‐charge‐limited carriers (SCLCs) into high density polyethylene (HDPE) is presented. Injected carriers are deeply trapped at crystalline‐amorphous boundaries before the steady state is reached. At elevated temperatures, they are thermally excited to the conduction band in the crystalline regions, and then hop with field‐dependent mobility through defect states of the amorphous regions. A hopping site separation of 2.2 nm, corresponding to 9.4×1019/cm3, yields good agreement with experimental current‐field characteristics for fields up to 0.5 MV/cm, in the temperature range 61–85.5 °C. The final currentIversus fieldFand temperatureTequation shows that the activation energy of the detrapping and transport processes are additive on a semilog plot ofI/Tvs 1/T. The total activation energy is 1.15 eV at 0.2 MV/cm, in agreement with others. The steady‐state field distributions in the sample are calculated, and are independent of temperature in the above temperature and field ranges. The conditions under which our theory reduces to that of simple SCLC, field‐independent mobility theory, and differences in conduction between linear low density polyethylene and HDPE are discussed.

ISSN:0021-8979    

DOI:10.1063/1.351335

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Ohmic contacts produced by high‐energy pulsed laser beam alloying Au/Te/Au/n‐GaAs are investigated by micro Raman spectroscopy. The results are compared to those from furnace annealed ohmic contacts. For the furnace as well as for the laser annealed ohmic contacts, no evidence for a doping of the contact region is found in the Raman spectra. The presence of a highly disordered GaAs surface layer is observed for both types of contacts. In addition, after furnace processing a Ga2Te3layer is formed. These results are consistent with earlier Mo¨ssbauer studies. For the laser alloyed samples the results strengthen the role of a defective/disordered interface structure where conduction might occur by a resonant tunneling process involving localized gap states.

ISSN:0021-8979    

DOI:10.1063/1.351336

出版商:AIP    

年代:1992

数据来源: AIP