摘要:

The quality of large semiconductor crystals grown from melts is significantly affected by the heat and mass transfer in the melts. The current understanding of the phenomena, especially melt convection, is reviewed starting from the results of visualization using model fluids or silicon melt, and continuing to the detailed numerical calculations needed for quantitative modeling of processing with solidification. The characteristics of silicon flows are also reviewed by focusing on the Coriolis force in the rotating melt. Descriptions of flow instabilities are included that show the level of understanding of melt convection with a low Prandtl number. Based on hydrodynamics, the origin of the silicon flow structure is reviewed, and it is discussed whether silicon flow is completely turbulent or has an ordered structure. The phase transition from axisymmetric to nonaxisymmetric flow is discussed using different geometries. Additionally, surface‐tension‐driven flow is reviewed for Czochralski crystal growth systems. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358882

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A wave optics approach to the calculations of the intensity distribution of an x‐ray point source image with a two‐dimensional (2D) focusing geometry is presented. Analytical formulas are derived to calculate the intensity distribution at the focal plane. This approach has taken into account the effects of x‐ray scattering within a 2D bent crystal, which includes the x‐ray refraction and absorption inside the crystal, and the effects of elastically deformed crystals described by the anisotropic elasticity theory. Based upon the elastic bending model, the modified Bragg law and 2D lens equations are discussed. In addition, the x‐ray extinction distance for curved crystals is found to be dependent on the size and the bending radius of bent crystals. For a monochromatic x‐ray point source, calculation of the intensity distribution with a 2D bent silicon crystal is given for both perfect and misaligned sources. The spatial resolution and the size of the image are determined. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358883

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Calculations and analysis of an extended x‐ray source image with a 2D focusing geometry are presented. Based upon the calculations for an x‐ray point source image (Paper Ia), theoretical expressions are derived which reveal the contributions from both the Bragg and the optical (Fresnel) diffractions to the intensity distribution of the image at the focal plane. That is, for a given focusing geometry, the intensity distribution of the image of an extended source consists not only of the crystal rocking curves for a bent crystal, due to the Bragg diffraction; but also of the optical diffraction, the Fresnel integral, due to the phase correlations of the thickness and the spatial extent of a doubly bent crystal. The contribution from the optical diffraction depends solely upon the bent crystal focusing geometry. The relationship between the source and the image at the focal plane is obtained, and the intensity distribution of an extended x‐ray source image with a 2D bent silicon crystal is given. ©1995 American Institute of Physics. 

ISSN:0021-8979    

DOI:10.1063/1.358884

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

An analytical model is presented to describe the influence of sample‐probe interactions on the shape of spectroscopic lines. By considering the discrete sampling of spatial property variations using a focused probe, the model predicts gradient‐induced line broadening, as well as probe channeling near free surfaces. The magnitude of sample‐probe interactions is governed by two system parameters: the probe size and the spatial property gradient. Furthermore, certain spatial heterogeneities are found to contribute appreciably to the signal and its associated line shape over distances several times the probe size. Experimental observations in fluorescence spectroscopy are used to evaluate the line‐shape model. Spectra measured along an embedded ruby fiber under a residual stress gradient are in good agreement with those calculated using the model. ©1995 American Institute of Physics. 

ISSN:0021-8979    

DOI:10.1063/1.358885

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The influence of optical feedback from coupled cavities on the reflective responses of absorption‐tunable Fabry–Pe´rot resonators has been examined and analyzed. The merits and improvements in performance of optical modulators utilizing the designs of coupled Fabry–Pe´rot resonators have been discussed. The variety of reflectivity responses available from coupled‐cavity Fabry–Pe´rot structures provides enhanced flexibility in device designs which minimizes the sensitivity of single‐cavity devices to variations in layer thicknesses and compositions, operating wavelength, and temperature. ©1995 American Institute of Physics. 

ISSN:0021-8979    

DOI:10.1063/1.358886

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A three‐dimensional Monte Carlo model is developed to simulate the thermalization process of atoms sputtered from the cathode in a glow discharge cell. A comparison is made with a simplified analytical thermalization model and the relative importance of different interaction potentials and scattering assumptions on quantities related to thermalization is investigated. Typical results of the thermalization model are (i) the thermalization profile (which gives the distribution of the thermalized sputtered atoms), (ii) the relative amount of atoms that can reach the backplate of the discharge cell without being thermalized, and (iii) the relative amount of backscattering to the cathode. The influence of gas pressure, kind of gas, and cathode material on the thermalization process is also investigated. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358887

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Experiments of deep‐level transient spectroscopy and transmission electron microscopy (TEM) observations have been carried out on heat‐treated &Sgr;=25 silicon bicrystals precontaminated with nickel before being heat treated at various temperaturesTa. For the lowestTavalue (600 °C), the electronic interface states were found to be shared between two overlapping narrow continua aroundEc−0.63 eV andEc−0.52 eV. Upon increasingTa, these states shift toward shallow positions and exhibit a marked tendency to shrink and to turn into a unique trap level. While the annealing at 900 °C has led to a single state atEc−0.50 eV, this later moved toEc−0.48 eV for 1000 °C and then toEc−0.44 eV for 1100 °C, with an accompanying consistent lowering in the barrier height (BH). TEM observations demonstrated the formation of pure type‐B NiSi2platelets for 800 °C, but indicated an increasingly important growth of type A for increasingly higherTavalues. While the existence of a unique trap level at highTacould be explained, like previous findings, by some ‘‘uniform’’ coverage of the boundary by the precipitates, the displacement of the interface state(s) toward shallower positions, together with the reduction of the potential barrier, are interpreted in terms involving the increasing contribution of A‐type plates with their low BH in addition to that of B‐type silicides with their high BH. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358888

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The effect of the annealing temperature on the optical and crystalline properties of 2 MeV Yb+ion‐implanted InP are systematically studied by photoluminescence (PL), photoluminescence excitation (PLE), selectively excited photoluminescence (SPL), and Raman scattering measurements. PL measurements present that the recrystallization of the implanted layers and the optical activation of Yb3+begin at 450 °C and 500–550 °C, respectively. It is demonstrated from the Raman experiments that there is a continuous restoration in radiation damages when the as‐implanted samples are annealed at temperatures between 450 °C and 550 °C. However, beyond 550 °C, the crystalline quality near the surface is shown to be degraded. For an explanation of this point, a comparison with optical micrographs is conducted. From the PLE spectra of Yb‐related luminescence, it is concluded that the highest crystalline quality of Yb+implanted layers could be achieved by annealing at 750 °C for 15 min. In the PLE spectra, a band observed earlier at 1.409 eV (8800 A˚) is recognized to be split into two peaks at 1.409 eV (8798 A˚) and 1.408 eV (8806 A˚), denoted by B1 and B2, respectively. A convictive assignment for these two peaks is proposed. Furthermore, an unusual broad band at 1.24 eV, which is observed only in SPL spectrum when the excitation is set on B1 energy, is described. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358889

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A simultaneous combination of scanning Kelvin probe microscopy and scanning atomic force microscopy has been applied to the problem of profiling dopant concentrations in two dimensions in silicon microstructures. By measuring the electrochemical potential difference which minimizes the electrostatic force between probe tip and sample surface, the work‐function difference between the tip and surface is estimated. To the extent that this work‐function difference is a consequence of the dopant concentration at or near the sample surface, doping profiles are inferred from the measurement. Structures examined and presented here include contact holes, and the technologically significant lightly doped drain of a metal–oxide–silicon field‐effect transistor. Using this methodology, one can distinguish relative changes in dopant concentration with lateral resolution less than 100 nm. Sample preparation is minimal, and measurement time is fast compared to other techniques. The measurements have been compared to predictions based on two‐ and three‐dimensional process and device simulation tools. The comparisons show that the technique is sensitive to changes in dopant concentration, from ≊1015to 1020cm−3, of less than 10% at these size scales. Suggestions to resolve absolute dopant concentration are made. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358819

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A microscopic many‐body model is proposed for the kinetics of metastable defects (MSDs) in hydrogenated amorphous silicon (a‐Si:H). It is based on the existence of short‐lived large energy fluctuations which induce transient traps for carriers that release their energy and enhance the creation or annihilation of MSDs. The expressions found for the photoinduced and thermally induced creation and annihilation rates’ coefficients explain the dependence on the variety of parameters. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358820

出版商:AIP    

年代:1995

数据来源: AIP