摘要:

A technique has been developed using an atmospheric pressure ionization mass spectrometer to measure the submonolayer equilibrium adsorption properties of moisture on tubing surfaces. This technique has been used to generate isobar data for moisture on 316 stainless steel surfaces with various commercially available surface treatments. Both a dissociated absorption model based on a Temkin energy distribution and a semiempirical adsorption model have been fit to the data. Though differences in the isobar data were clear, moisture absorption did not vary strongly with tube surface treatment. The implications of these results on tubing dry‐down dynamics were confirmed by running controlled dry‐down tests from an initial level of 200 ppb using an inlet gas at 0.2 ppb. The ranking of dry‐down times (fastest to slowest) was the same as predicted by the isobar data. The difference between the dry‐down time of the fastest and slowest responding tubes was approximately a factor of 4.

ISSN:0734-2101    

DOI:10.1116/1.579089

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Measurements of ion‐induced electron emission have been performed with helium and argon ions with energies between 300 and 900 eV on W, W with 10% Ti, Al, Al with 1% Cu, Al with 1% Si, Si, and Be. This article describes many of the important surface characteristics that influence the ion‐induced electron emission. For low‐energy ions, the substrate material was found to be less important as the velocity of the incident ion decreased. In the case of incident Ar+the substrate material had a negligible effect on the emission for this energy range. The presence of an adsorbed layer enhanced emission in all cases. Heating the substrates resulted in oxidation of the surfaces and a subsequent increase in emission. The electron emission from aluminum samples with smaller grain sizes was higher than samples of identical composition with larger grains. This effect is due to the greater number of adsorption sites resulting from the higher grain boundary area.

ISSN:0734-2101    

DOI:10.1116/1.579090

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The effects of a gas‐phase polysulfide treatment on InP were studied by x‐ray absorption near‐edge structures (XANES) of both the sulfurL‐edge andK‐edge, and by x‐ray photoelectron spectroscopy (XPS). Some passivated InP samples were encapsulated with about 4 nm of remote plasma deposited silicon nitride, and the chemical structure of the sulfur atoms at the interface was again determined by angle dependentK‐edge XANES. Both XPS andL‐edge XANES confirmed the presence of indium to sulfide bonding on the surface exposed to gas‐phase polysulfide, and XPS confirmed the presence of more than one sulfide species. The angle dependence inK‐edge XANES indicated that most of the surface sulfur atoms had their sigma bonds oriented along the (110) azimuth with a polar tilt angle of about 40°–60°. It is thus plausible that these sulfur atoms terminated the indium atoms on InP (100) in the form of In–S–In bridging bonds along the (110) azimuth. Vacuum annealing was found to cause desorption of some surface sulfide species and conversion of the residual sulfide species into one sulfide species, and to enhance the XANES angle dependence which again indicated the presence of the In–S–In bridging bonds along the (110) azimuth. Further angle dependentK‐edge XANES analyses showed that such a sulfur bonding configuration was preserved even after the gas‐phase polysulfide passivated InP surface was capped with silicon nitride deposited by remote plasma chemical vapor deposition.

ISSN:0734-2101    

DOI:10.1116/1.579091

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

A high‐resolution quadrupole mass spectrometer (QMS) which can detect3He in HD and4He in D2has been developed. The QMS is equipped with two resolving powers, i.e., a high‐resolution mode and a normal one, and voltages for realizing the two modes are supplied by a common circuit. The high‐resolution mode adopts a condition of the second stability zone (zone II) in the Mathieu diagram and can analyze a range of 1–9 amu. The detectable peak ratios of3He/HD and4He/D2were obtained at roughly 0.1 and 10−4, respectively. The normal mode adopts the first stability zone (zone I) and has an analyzable range of 1–60 amu.

ISSN:0734-2101    

DOI:10.1116/1.579093

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

This article presents the main features in the design of vacuum systems for electron cyclotron resonance (ECR) ion sources. It is very interesting to consider them as a possible source of high‐charge‐state ions in upgrading present heavy‐particle accelerators. Scaling relationships are given as a basis for understanding the vacuum configurations of ECR ion sources. The relevance of gas desorption effects to vacuum equilibrium and stability is also pointed out. Ion‐induced pressure instability, a model of hydrogen diffusion, and the influence of neutral gases on the vacuum stability of ECR ion sources are discussed.

ISSN:0734-2101    

DOI:10.1116/1.579094

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The structure of TiNxfilms formed by low energy ion‐assisted deposition has been investigated by electron microscopy techniques. A dual ion beam system was used for the deposition with two Kaufman sources; one producing a 1 keV beam for sputtering Ti, the other a 100–400 eV argon or nitrogen ion beam. The variables of the experiment are the ion energy (100–400 eV), ion species (Ar+or N+2), ion/atom arrival ratio, the angle of incidence of the ions with respect to the film and the partial pressure of nitrogen during deposition. The structure of the films has been examined using a 200 keV electron microscope for production of electron diffraction patterns and bright and dark field images of the films. It is found that films formed by reactive sputtering (i.e., no ion bombardment) are single phase TiNxwhich has fcc structure. The grain sizes of the microcrystals, which are randomly orientated, are 10–15 nm. Ion bombardment during deposition generally leads to strong preferential (100) orientation of the microcrystals parallel to the surface of the film and this is coupled with a reduction in the grain size of the microcrystals in the film. Grain growth also appears to take place approximately along the direction of bombarding ions. Results suggest that the degree of orientation depends on the added energy per atom during deposition, indeed there seems to be an energy ‘window’ within which strong, preferred orientations are observed.

ISSN:0734-2101    

DOI:10.1116/1.579095

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

A new method of preparation of oxide thin films is presented in this paper. The method consists of the bombardment of a substrate with accelerated O+2species while a flow of a volatile organometallic precursor is directed on its surface. This ion beam induced chemical vapor deposition procedure (IBICVD) has been used to prepare TiO2thin films from Ti(CH3CH2O)4as a precursor. Also, for comparison, TiO2thin films have been grown by a plasma assisted chemical vapor deposition (CVD) method. A study of the growing process has been carried out by x‐ray photoelectron spectroscopy (XPS), while the films have been characterized by XPS, scanning electron microscopy, transmission electron spectroscopy, and UV‐visible (UV‐vis) spectroscopy. Values of the refraction index of the TiO2films prepared by IBICVD are similar to those of other TiO2prepared by ion beam assisted methods as given in the literature, but superior to those of the films grown in the present study by plasma assisted CVD.

ISSN:0734-2101    

DOI:10.1116/1.579096

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

During ion‐assisted deposition of TiN using Kaufman sources the pressure in the substrate chamber can rise to about 10−2Pa. This leads to charge‐exchange collisions and as a result, a component of fast neutral atoms in the energetic beam. This paper considers the transport of 100–500 eV Ar+or N+2ions through a gas mixture of argon and nitrogen of known composition. Charge exchange cross sections for N+2→N2, Ar+→Ar, Ar+→N2, and N+2→Ar reactions have been used to calculate the neutral component of the beam. The results show that the neutral component is only weakly dependent on the primary ion energies and ion species. The magnitude of this component for a constant total pressure of 3×10−2Pa varies between 10% and 60% as the partial pressures of nitrogen (and argon) vary between 1 and 3×10−2Pa.

ISSN:0734-2101    

DOI:10.1116/1.579097

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

This article describes a new high‐power fast atom beam (FAB) source incorporating an electromagnet. The electromagnet increases the total path length of electrons entering the source, enabling this source to produce higher plasma densities. Beam current densities up to 1 mA/cm2, which is about ten times that of a conventional FAB source, are obtained by using an electromagnet and a multiaperture grid. The beam current density can also be controlled by adjusting the flux density of the electromagnet and the gas pressure in the source. The beam neutralization coefficient is more than 90% almost independent of the flux density, discharge current, and source configuration. This coefficient does, however, strongly depend on the gas pressure of the FAB source, rapidly increasing as gas pressure increases. Most of the fast atoms have a kinetic energy about equal to the discharge voltage. Ions generated in the glow discharge are accelerated, and collisions with gas molecules near the cathode convert these ions into fast atoms without loss of kinetic energy.

ISSN:0734-2101    

DOI:10.1116/1.579098

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

A numerical algorithm and simulation results are presented for microscopic profile evolution of material surfaces subject to plasma etching (reactive‐ion etching) and surface passivation. Surface evolution is calculated by the shock‐tracking method, which accurately simulates formation and evolution of facet corners. The angle distribution for the reemission of sputtered materials is assumed to follow an arbitrary cosine law (i.e., ∝cosβ Θ, with Θ being the reemission angle and β≳0). Thickness of sidewall passivation layers and resulting etched profiles are shown to depend sensitively on both the reemission angular distribution and the sticking coefficient.

ISSN:0734-2101    

DOI:10.1116/1.579099

出版商:American Vacuum Society    

年代:1994

数据来源: AIP