摘要:

A self‐consistent, one‐dimensional simulator for the physics and chemistry of radio frequency plasmas is developed and applied for CF4. The simulator consists of a fluid model for the discharge, a commercial Boltzmann code for calculations of electron energy distribution function (EEDF), a generalized plasma chemistry code, and an interface among the three models. Chemistry calculations are fed back into the physics model and the procedure is repeated until a self‐consistent solution is obtained. The CF4discharge shows an electronegative behavior with ten times more negative ions than electrons even at low pressures of 100 mTorr. The EEDF high energy tail lies between the Maxwell and Druyvensteyn distribution. The chemistry model predicts densities of 3.5×1012cm−3for CF3, 3×1012cm−3for CF2, 2.5×1013cm−3for F, and 0.7×1012cm−3for CF, in agreement with experimental data from a Japanese group. CF and to a lesser extent CF2, are consumed at the surface, and CF, CF2, and F densities and profiles are sensitive to the sticking coefficient and residence time. CF2and CF are produced mainly from the parent gas CF4and not its fragments. Finally, the chemistry results are fed back into the physics model and influence the discharge structure, mainly by changing electron densities and the width of the inner core of the positive‐negative ion plasma. Thus, the importance of self‐consistent plasma calculations is demonstrated and justified. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359143

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The spatiotemporal structure of O2rf discharges between parallel plates at 13.56 MHz is investigated by using the relaxation continuum model. The results for pressure of 0.5 Torr and the sustaining voltage of 75–200 sin &ohgr;tV are studied by considering the elementary particles, O+2, O+, O−2, O−, electrons, and O in O2. In these conditions, atomic oxygen, formed by the dissociative electron impact in O2with density of ∼1014cm−3, plays important role to the rf structure through the associative detachment process. That is, the expanding characteristics of the sheath width unique to the O2rf discharge are realized with increasing the sustaining voltage. The validity of the numerical result is demonstrated with the spatiotemporal structure by the measurement by the spatiotemporally resolved optical emission spectroscopy. The flux of each particle to the electrode is also discussed. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359144

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Electron densities between the electrodes of a flashover anode intense ion beam diode are studied with laser interferometry. Visible and infrared data show no measurable density near the anode and at mid‐gap during ion beam emission. Hence, anode or cathode plasma closures do not cause impedance collapse. However, a two‐phase density build‐up observed near the cathode during beam emission appears associated with impedance collapse and with the termination of the ion beam. Substantial density is measured after the end of the ion beam, consistent with ionization of the neutrals produced by the flashover process. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359145

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Silicon carbide is a semiconductor material suitable for a variety of specialized devices. Implantation profiles of 30–300 keV B, Al, N, and As in 6H&agr;‐SiC are reported. The profiles, measured by secondary‐ion‐mass spectrometry, are fit with Pearson‐IV curves which require knowledge of the first four moments of the distribution. The moments of the impurity distributions are extracted from the experimental data and fit to simple functions of the ion energies. Thus, an accurate implantation depth profile simulator, based on experimental data for the common dopants in 6H&agr;‐SiC, is developed. This method results in a more accurate implant simulator than is obtained using conventional first‐principles calculations, primarily due to channeling considerations. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359146

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Orientation selection in platinum films of ∼20 nm thickness deposited onto (001) MgO substrates bye‐beam evaporation was investigated through ion beam channeling and x‐ray diffraction. A mixture of crystallites having (111) and (001) orientation was observed in Pt films deposited over a range of substrate temperatures from 25 to 700 °C, with the (111) orientation dominant at low temperatures. The (111) orientation was present in these evaporated films at significantly higher substrate temperatures than reported for Pt films deposited by sputtering or pulsed laser deposition. Both orientations had strongly preferred in‐plane orientations: [110] Pt//[110] MgO for the (001)‐oriented crystallites and [110]Pt//[110] MgO for the (111). The orientation selection process was rationalized based on the expected relative interfacial energies for these two orientations. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359147

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The activation energy for thermal dissociation of hydrogen from silicon dangling‐bond defects (Pbcenters) has been measured using both (111)‐ and (100)‐oriented samples. The behavior of each of the threePbvarieties [P111bat the (111) interface,P100b0andP100b1at the (100) interface] is compared. ForP111b, excellent agreement with previous results by Brower [Phys. Rev. B42, 3444 (1990)] is obtained. The activation energies of the (100)‐interfacePbcenters are slightly higher, assuming the same vibrational frequency, and, unlike that ofP111b, are affected by a postoxidation anneal. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359148

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

This article describes the results of a surface morphology study of photodeposited thin film devices of Selenium by scanning force microscopy (SFM). First, the structures of the photodeposited films were investigated at device level dimensions of the order of visible wavelength. Specifically, ultrathin sinusoidal holographic gratings with spatial periods in the range 480–514 nm were visually identified from SFM nanograph images. Second, grain level structural investigation was performed using image processing techniques such as filtering and one‐ and two‐dimensional Fourier transforms analysis. The variation of the surface grain structure was sampled across the Gaussian profiles of the laser photodeposited patterns. It was found that the random amorphous clustering at the perimeter of the deposited structures becomes progressively grainy towards the center, creating protrusions above the surface with trigonal Selenium (t‐Se) crystalline features. Third, performing image enhancement analysis at high magnification—the nanometer level structure was investigated for amorphous Selenium (a‐Se) and the laser thermally induced structural transformations of thea‐Se films. It was found that the atomic solid‐state structure ofa‐Se films, previously deduced only by indirect methods, consists mainly of a random mixture of Sexbranched chains containing also a small concentration of imperfect ring structures characteristic of the &agr;‐ and &bgr;‐monoclinic phases. The triclinic crystalline phase (t‐Se) was identified in the center of the laser overheated regions of the film Gaussian profile. The results enable us to conclude about the debate in the literature regarding the crystalline and amorphous structure of Selenium thin films. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359149

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Nanocrystalline Fe73.5Cu1Nb3Si13.5B9alloy prepared by the crystallization of amorphous alloy has been studied by using the positron annihilation technique. Positron parameters, i.e., lifetime &tgr;1, &tgr;2, and line shape parameterSare obtained as a function of the annealing temperature. The results show that there exist two types of defects at the interfaces of nanocrystalline Fe73.5Cu1Nb3Si13.5B9alloy: vacancy‐like and vacancy‐like group microvoids characterized by the lifetime &tgr;1and &tgr;2. The former is in overwhelming majority. The changes of the structural defects corresponding to different stages, structural relaxation, and crystallization are discussed. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359150

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The origin of misfit dislocations in significantly relaxed low‐misfit strained layers is considered. The characteristics of strain relief due to heterogeneous dislocation nucleation at particles, nucleation of dislocations at the free surface of the layer, and multiplication mechanisms are considered and compared with the observed relaxation behavior of constant composition layers of InxGa1−xAs layers on (001) GaAs. It is proposed that dislocation multiplication is consistent with a wide range of experimental results. The observation that 60° and edge dislocations are often seen lying above, but parallel to, the interface in significantly relaxed layers has prompted a study of the possible multiplication mechanisms that they may form. It is shown that one in four reactions between 60° dislocations may lead to a pair of spiral dislocation sources, and that a single spiral source that operates only once may form at the end of edge dislocations. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359151

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Structure of stacking faults formed in pairs in a ZnSe epitaxial layer grown by gas source molecular beam epitaxy on a GaAs(001) buffer layer was determined with transmission electron microscopy. Extrinsic type stacking faults were formed on (111) and (1¯1¯1) planes with the same polarity, which was determined by convergent‐beam electron diffraction. The two stacking faults meet at a point which is a few atomic layers away from the interface between ZnSe and GaAs. Partial dislocations at the edge of the stacking faults were found to be the Shockley type ones with a Burgers vector of 1/6⟨211⟩. Probable formation processes of the stacking faults have been discussed. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359152

出版商:AIP    

年代:1995

数据来源: AIP