摘要:

We have bombarded single crystal (100) and (111) silicon with a hydrogen ion beam produced by a Kaufman ion source. A range of dose rates from 0.2–2.0 mA/cm2, bulk sample temperatures from 35°–350° C, and doses of 2×1017, 2×1018, and 2×1019ions/cm2at maximum ion energies of 1600 eV was explored. Transmission electron microscopy and electron spin resonance measurements were used to characterize the bombarded samples. Extensive microstructural modifications occur as a result of hydrogen ion bombardment; the orientation, size, density, and distribution of the features which form vary as a function of crystal orientation, dose rate, bulk temperature, and total dose. Electron spin resonance studies indicate no detectable change in the number of occupied unpaired electron spin states occur in conjunction with this damage.

ISSN:0734-2101    

DOI:10.1116/1.573201

出版商:American Vacuum Society    

年代:1985

数据来源: AIP

摘要:

The adsorption of D2O and O2on polycrystalline FeTiO3(natural ilmenite) has been studied by x‐ray photoelectron spectroscopy. Oxygen was found to absorb reactively with Fe0on Ar+‐sputtered surfaces at and above 150 K while D2O was found to adsorb molecularly or in ice layers below 170 K on both Ar+and O+2ion‐bombarded ilmenite. The D2O desorbs at 170 K with either the formation of an OD complex or a strongly bound molecular layer of water.

ISSN:0734-2101    

DOI:10.1116/1.573248

出版商:American Vacuum Society    

年代:1985

数据来源: AIP

摘要:

Magnetically enhanced sputtering configurations suited to the dc sputter deposition of ferromagnetic materials at a high rate are discussed. The characteristics of two different types of sources are described and compared with those of a conventional planar magnetron of similar size and construction.

ISSN:0734-2101    

DOI:10.1116/1.573178

出版商:American Vacuum Society    

年代:1985

数据来源: AIP

摘要:

The axial‐emission ionization gauge (AEG) has been modified to form an axial‐emission magnetron ionization gauge (AEMG) by adding an axial magnetic field to the electrode construction of the AEG. This modification results in a much lower limiting measurable pressure. AEMG gives performances like that of Lafferty’s hot‐cathode magnetron ionization gauge (LHMG) but the ratio of the x‐ray photocurrent to the anode currentIx/Iais smaller by more than two orders, so its lower limit is lower than that of LHMG. The upper limit of measurable pressure can be extended to 1.33×10−2Pa (1×10−4Torr) by operating the AEMG without the magnet. Since the electrode construction of AEMG is very simple, it is easy to de‐gas and this is of benefit to its operation under extremely high vacuum.

ISSN:0734-2101    

DOI:10.1116/1.573187

出版商:American Vacuum Society    

年代:1985

数据来源: AIP

摘要:

This paper deals with the continuation of research on vacuum pumping with 60 Hz ac voltages and permanent magnets arranged to form a crossed‐field configuration. It is well known that dc voltages in a crossed‐field discharge and in the presence of a titanium cathode will cause a decrease in residual gas pressure. In our previous research it was demonstrated that this result could also be achieved with 60 Hz ac voltages. Before applying this knowledge to commercial vacuum pumps it is important to gain an understanding of the underlying physical mechanisms. Of particular interest are the initiation and maintenance of the discharge under ac conditions. Results reported in this paper deal with a radial magnetic field in the butt‐gap between parallel disk electrodes. In this particular crossed‐field arrangement, it was found that the electron space charge is unstable, but ion production is more or less continuous with both dc and ac excitation. The pumping yield per ion was found to be low, but could probably be increased by replacing the glass tube with a metallic vessel so that fewer of the sputtered titanium atoms combineinsituwith adsorbed gas molecules on the glass wall.

ISSN:0734-2101    

DOI:10.1116/1.573197

出版商:American Vacuum Society    

年代:1985

数据来源: AIP

摘要:

We have calculated the optical absorption coefficient due to interband transitions between quantized subbands in the valence and conduction bands of a thin semiconducting quantum well wire having a direct energy band gapEg. The model we have used in our calculations assumes electron wave functions and energy eigenvalues of the particle in a box type for the motion of the carriers in the direction perpendicular to the axis of the thin semiconducting wire. The threshold for the optical absorption due to interband transitions is shifted to shorter wavelengths as the cross‐sectional area of the wire decreases. Above the threshold, the absorption is an oscillatory function of the photon energy when the transverse dimensions of the wire are fixed. For allowed transitions, the selection rules allow transitions only between those subbands in the conduction and valence bands having the same set of quantum numbers. In this case, the absorption coefficient has peaks whenever the photon energy is such that transitions can take place between new pairs of subbands in the valence and conduction bands. The absorption coefficient for such allowed transitions is directly proportional to the density of states of the carriers in the valence and conduction bands. For forbidden transitions, the threshold for the beginning of absorption is also shifted towards shorter wavelengths because of size quantization and the absorption is an oscillatory function of photon energy for fixed transverse dimensions of the wire, but the selection rules for transitions allow transitions to states where the quantum numbers of the quantized subbands can be different in the conduction and valence bands. Also, when the transitions are forbidden, the behavior of the absorption depends upon the polarization of the radiation relative to the axis of the quantum well wire.

ISSN:0734-2101    

DOI:10.1116/1.573208

出版商:American Vacuum Society    

年代:1985

数据来源: AIP

摘要:

New electrical conductivity and dielectric data for D–T gas at room temperature and densities of 10 to 120 mol/m3at 1592 Hz are reported. These plus earlier cryogenic gas and liquid data are reinterpreted in terms of space charging, which is present in almost all samples. This effect concentrates electric charge near the plates to cause an excess dielectric constant, and it also diminishes electrical conductivity by cancelling much of the external electric field. The mobilities of electrons and ions, plus their recombination coefficients, are included in the model. The effect of the 1592 Hz signal is also considered. Gas phase results are consistent with the presence of electrons, but the liquid may contain both electrons and negative ions.

ISSN:0734-2101    

DOI:10.1116/1.573241

出版商:American Vacuum Society    

年代:1985

数据来源: AIP

摘要:

In order to supply and recover hydrogen isotopes in small high vacuum systems, reversible pumps using ZrNi hydride as a getter material have been developed. Since the PC isotherms for the ZrNi–hydrogen system have two different plateau pressures corresponding to the existence of mono‐ and trihydrides, it is possible for the getter pumps to have two different equilibrium pressures. Because of the rapid decomposition kinetics of ZrNi hydride, these getter pumps are fast and consume little electric energy to supply hydrogen isotopes to high vacuum (HV) systems, e.g., it requires only 3.8 Wh and 150 s from onset of heating to supply 240 Torr liter (200 Torr×1.2 liter) D2gas. One of the significant features of this getter pump is that, once activated, the gettering action proceeds at room temperature. Using a combination of two ZrNi hydride getter pumps having two different equilibrium pressures, it is possible to recover hydrogen isotopes completely from HV systems, e.g., 10 Torr D2gas in a 1.2 liter glass HV system, can be pumped to 1×10−4Torr within 200 s.

ISSN:0734-2101    

DOI:10.1116/1.573242

出版商:American Vacuum Society    

年代:1985

数据来源: AIP

摘要:

In a high vacuum particle wall, collisions occur much more frequently than in mutual elastic ones, therefore, chaotization (Maxwellization) does not take place. Hence, the gas‐phase state is determined by boundary conditions, i.e., surface scattering processes. In this paper, steady‐state equations of low‐density (molecular regime) gas, based on probability distribution functions of adsorption, desorption, and reflection, have been derived. Calculations performed for spherical and planar symmetry show that rarefied gas can be strongly nonuniform and anisotropic; deviations from homogeneity can reach one order of magnitude. The idea of experimental verification has been proposed. off

ISSN:0734-2101    

DOI:10.1116/1.573243

出版商:American Vacuum Society    

年代:1985

数据来源: AIP

ISSN:0734-2101    

DOI:10.1116/1.573244

出版商:American Vacuum Society    

年代:1985

数据来源: AIP