摘要:

Film growth on glass fibers (40 &mgr;m diameter) is used to probe the distribution of SiH4decomposition products that producea‐Si:H films in silane rf glow discharges. The film thickness on fibers spanning the electrodes is measured versus position to map the spatial variation of the film‐precursor (radical) density. The optical emission from the discharge, which is shown to be essentially equivalent to the distributed source of SiH4decomposition products, is compared to the density maps. This comparison shows that the SiH3radical dominates deposition, that this SiH3is produced in the optically bright regions of the discharge, and that H atoms react rapidly with SiH4before diffusing significant distances in the discharge. The perturbative nature of the probes on the discharge environment is also addressed.

ISSN:0021-8979    

DOI:10.1063/1.345292

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Laser‐induced fluorescence (LIF) excitation and time‐resolved LIF spectroscopy have been used to explore the interaction of a nitrogen plasma with a metal surface. The rotational temperature, the concentration of N+2, and the lifetime of N+2(B2&Sgr;+u)&ugr;=0 were measured as a function of distance from the metal surface. It was observed that the lifetime of the excited ion decreases sharply in the plasma sheath which is created in front of the metal surface. The concentration of N+2(X 2&Sgr;+g), which was measured simultaneously with the lifetime of excited N+2, indicates a quasilinear decrease from the cathode to the grounded surface.Trotundergoes a gradual reduction from the bulk plasma up to the surface where its value is a good approximation of the surface temperature. An interpretation of these phenomena including a numerical simulation of the lifetime decrease is proposed here. The calculated values are in good agreement with experimental results. The dependence of lifetime decrease on the sheath potential as well as on other important parameters (cross section, profile of the electric field) is further discussed.

ISSN:0021-8979    

DOI:10.1063/1.345293

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A model for an abnormal glow discharge, including a self‐consistent analysis of the cathode fall, was developed. It combines microscopic particle simulation by means of Monte Carlo methods with a fluid model of the gas discharge. The model allows calculations of the steady‐state electrical field distribution, the charged‐particle densities, and the current densities along the axis of the discharge. The model was used to simulate a glow discharge in 80% He and 20% SF6at a pressure of 8 Torr with a current density of 1 A/cm2. The computed discharge voltage agrees well with measured values. The computer code can easily be modified to describe the charged‐particle densities and energies not only in the cathode fall region, but in any plasma boundary layer.

ISSN:0021-8979    

DOI:10.1063/1.345294

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Hard amorphous films ofa‐C:H anda‐C:D were deposited by a rf glow discharge in either CH4or CD4. By ion bombardment with protons and deuterons, the H/D exchange process was studied as function of the bombardment fluence by means of depth profile measurements. The local hydrogen and deuterium contents are not adding up to a constant ‘‘saturation’’ value: the local mixing model is not valid. Instead of that an initial depletion appears, which depends on the incident energy of the ions. At higher fluences, the total (H+D):C ratio tends to increase again, due to an increasing influence of the deposition process. This demonstrates a structural difference betweena‐C:H films and hydrogen‐saturated layers of implanted carbon.

ISSN:0021-8979    

DOI:10.1063/1.345296

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We present a theoretical treatment and experimental data for the dynamical behavior of a cholesteric liquid crystal submitted to uniaxial dilative strains applied along the helical axis. The results show the importance of the permeative contribution in the transient regime before a new equilibrium state is found where the apparent pitch is varied.

ISSN:0021-8979    

DOI:10.1063/1.345276

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Neutron and proton irradiations have been performed on self‐aligned GaAs metal‐semiconductor field‐effect transistors (MESFETs) and resistors utilizing shallow ion‐implanted channels. FET threshold voltage shifts during irradiation were lower than reported elsewhere (less than 115 mV for a −0.85 V threshold FET irradiated by 4.3×1014neutron cm−2). This is shown to be explained by the shallow active layers used. A neutron carrier removal rate between 20 and 25 cm−1is necessary to fit the FET data. Carrier removal rates derived from resistor damage were 150 cm−1for peak doping levels of 4×1017cm−3, greatly in excess of those derived from epitaxial or bulk GaAs resistors, and inconsistent with values obtained from threshold shifts of FETs with identical active layers. Resistor and FET threshold voltage changes for 52 MeV proton irradiation were nearly an order of magnitude greater than for an equivalent dose of 1 MeV (Si) neutrons. The extrapolated worst‐case failure dose of direct‐coupled FET logic inverters was better than 1.8×1015neutron cm−2despite the limited noise margins of this logic scheme.

ISSN:0021-8979    

DOI:10.1063/1.345277

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Measurements of the relevant anisotropic part of the dielectric constant for ferroelectric liquid crystals allows a calculation of the dielectric torque acting upon the director during addressing conditions in a matrix‐multiplexed device. The frequency dependence of the dielectric anisotropy is presented for different commercially available ferroelectric liquid‐crystal materials in the range 103–106Hz. The field dependence of the switching time has been measured for one of the materials in order to determine the field at the minimum value. The ratio between this field and the field at which switching ceases has been determined and found to be in good agreement with the theoretically calculated value. The results enable us to consider the torque balance as a function of field and frequency, and thereby identify appropriate driving conditions.

ISSN:0021-8979    

DOI:10.1063/1.345278

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We have synthesized ion scattering analysis programs for studying surface and interface structures. The probing ion energies can be selected in a wide energy range from 10 keV up to several MeV. One of the present programs allows the simulation of both random and aligned spectra from perfect or partially disordered heteroepitaxial films. For defect profiling, the following types are available: (1) asymmetric Gaussian, (2) exponential reduction shape, and (3) step function. Another is used to analyze the structures of islands formed on the top surfaces of substrates. The targets have basically multielemental and multilayered structures comprising the units of amorphous/single crystal. These simulation programs are applied to disorder profiling of Ar+‐implanted LiNbO3, mechanically polished Mn‐Zn ferrite, and GaAs/Si heteroepitaxial films, and to characterizing the Cu‐Si islands on Si substrates.

ISSN:0021-8979    

DOI:10.1063/1.345279

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Structural properties of graphitized polyperinaphthalene (GPPN) fiber were investigated with transmission electron microscopy. The GPPN fiber has a rectangular cross section consisting of two different kinds of thin and linear sheets of graphite. One graphite sheet with 5–50 layers of graphite is linearly extended normal to the direction of the fiber axis with thecaxis almost parallel to the fiber axis. The sheets bend at the sides of the fiber forming a continuously joined folding structure. Another type of graphite sheet which is extended to the direction parallel to the fiber axis exists at the four edges of rectangular GPPN.

ISSN:0021-8979    

DOI:10.1063/1.345280

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The study of deep level semiconductor defects frequently employs deep level transient spectroscopy (DLTS), a technique developed for structures with constant doping concentration profiles. In this paper, the theory of the DLTS measurement is extended to the more general case in which both the doping profile and the trap profile vary with depth. This analysis yields a method of calculating exact DLTS transients for the general case, and by its application to several examples, demonstrates that the doping profile shape and the measurement conditions are both factors which determine the degree to which the DLTS transient can be approximated by an exponential. The structures which do exhibit approximately exponential DLTS transients include several which arise in the course of device processing. This study shows that in such structures, a knowledge of the doping profile and the general form of the trap profile can be combined with the standard DLTS boxcar sampling method to obtain trap profile information in addition to the trap activation energy and capture cross‐section data.

ISSN:0021-8979    

DOI:10.1063/1.345281

出版商:AIP    

年代:1990

数据来源: AIP