摘要:

Using a computer simulation technique with a semiempirical potential, a Si crystal was cleaved along the (111) plane. The π‐bonded chain structural features of the Si(111) cleavage surface are observed and found to be a consequence of the dynamics of this cleavage process and seem not to be influenced by the final energetics.

ISSN:0734-2101    

DOI:10.1116/1.574147

出版商:American Vacuum Society    

年代:1987

数据来源: AIP

摘要:

Postsputtering ionization using an inert gas plasma to decouple the sputtering and ionization processes minimizes matrix effects commonly associated with conventional secondary ion mass spectrometry. Glow discharge mass spectrometry (GDMS) utilizes ions generated in a dc inert gas plasma to sputter atoms into the ambient plasma from the surface of a cathode composed of the material to be studied. The sputtered atoms, predominantly neutral, are then ionized in the plasma by Penning and electron impact ionization. GDMS provides excellent sensitivity and signal stability, and has found wide uses for characterization of bulk materials such as metals and GaAs. The sensitivity and large sampling volume also make it ideal for determining nonuniform trace contaminants in materials, e.g., U and Th in metals. Sputtered neutral mass spectrometry uses either low‐energy plasma ions (direct bombardment mode or DBM) or an independent focused ion beam (separate bombardment mode or SBM) to sputter atoms into a low‐pressure high‐frequency plasma for electron impact ionization. DBM offers better depth resolution than conventional surface analytical techniques and is ideal for thin‐film studies. The plasma electrons compensate for sample charging in SBM and make this method ideal for the analysis of insulating material such as phosphosilicate glass.

ISSN:0734-2101    

DOI:10.1116/1.574148

出版商:American Vacuum Society    

年代:1987

数据来源: AIP

摘要:

The Auger spectra of the polar and prism surfaces of single‐crystal ZnO were measured. The sensitivity factors derived from the differentiated spectra are 0.26 and 0.25 for a beam energy of 3 and 5 keV, respectively. These values agree fairly well with the theoretical calculations of Mroczkowski and Lichtman.

ISSN:0734-2101    

DOI:10.1116/1.574149

出版商:American Vacuum Society    

年代:1987

数据来源: AIP

摘要:

A numerical method is proposed for estimating the production yields of C2and C3hydrocarbons, which are generated by bombarding graphite with hydrogen ions, from signal intensities of a quadrupole mass spectrometer (QMS). It is shown that the C2H2, C2H4, C2H6, C3H4, C3H6, and C3H8production yields can be easily estimated by fitting the calculated intensities of QMS signals, by means of summing up the crackings of species, to the measured ones, whose masses range between 24 and 44. The derived formulas can uniquely determine the yields, using the measured data of the cracking coefficients and sensitivities of purified standard gases for the QMS as well as of the intensities of QMS signals.

ISSN:0734-2101    

DOI:10.1116/1.574150

出版商:American Vacuum Society    

年代:1987

数据来源: AIP

摘要:

The heavier isotopes of a given element are generally underrepresented in the secondary ion mass spectrometry mass spectrum since they emerge from the sample with lower average velocity and are therefore less likely to be emitted as ions. The relative deviation of an isotope ratio measurement from its expected value is represented in the literature by the parameter α. In this work we report measurements of α as a function of secondary ion energy in high‐purity Ge, Mo, Pd, Cd, Sn, and W samples; each of which offers several abundant isotopes for examination. A Cameca IMS‐3f magnetic sector instrument is operated in the high‐energy resolution mode for these measurements. The α values are determined from weighted least‐squares fits to the isotope ratio deviations. Appropriate precautions against beam instability, mass interference, and detector saturation effects are employed. Positive and negative ion emission, induced by O+2and Cs+bombardment, respectively, are examined. For monatomic positive ion (M+) emission, the magnitude of α correlates roughly with the secondary ion yields and generally increases with increasing emission energy. In contrast, α values for oxide species (MO+) display an inverse dependence on energy indicating surface emission. For negative ion (M−) emission, α changes sign at low energies indicating that, at low energy, ion emission is dominated by the survival probability of the negative ion while, at higher energies, emission depends on the probability of ion formation by electron attachment. Measured α values for diatomic (M+2, M−2) emission are examined with respect to current models of molecular ion formation.

ISSN:0734-2101    

DOI:10.1116/1.574151

出版商:American Vacuum Society    

年代:1987

数据来源: AIP

摘要:

The analysis of shallow, steeply varying profiles, using secondary ion mass spectrometry with quadrupole and magnetic sector instruments, is described. The problems in generating a reliable profile, free of transient effects, and ion beam induced displacements and broadening effects, in both types of instruments are discussed. The most important conclusion is that one should be capable of varying the primary beam energy, primary mass, the angle of incidence, and the polarity of the secondary ions independently of each other. We also report the use of special experimental conditions which circumvent some of the problems posed in magnetic sector instruments; low‐energy Cs beams (down to 1 keV) are used in combination with sensitive detection of positive secondary ions. Finally, it is shown that for a 5‐kV As+implanted Si specimen all the projected ranges and decay lengths of the profiles, measured with different primary masses, angles of incidence, and primary energies, can be correlated in a universal curve which has the penetration depth of the primary ion as the basic parameter. The effect of the ambient pressure on the results is also described.

ISSN:0734-2101    

DOI:10.1116/1.574152

出版商:American Vacuum Society    

年代:1987

数据来源: AIP

摘要:

A large distortion in the secondary ion mass spectrometry depth profile in GaSb is found under cesium‐ion bombardment. The result is interpreted in terms of a nonuniform sputter removal near the initial surface. On the cesium‐ion‐bombarded GaSb surface, microcrystalline GaSb growth takes place to upheave the bombarded region up to 0.1 μm from the initial surface in the very early stage of cesium‐ion bombardment. Above a cesium‐ion dose of 1×1017 ions cm−2, the normal sputtering rate versus ion dose was obtained. This phenomenon is thought to be the cesium induced microcrystal growth specific to the stoichiometric GaSb surface.

ISSN:0734-2101    

DOI:10.1116/1.574153

出版商:American Vacuum Society    

年代:1987

数据来源: AIP

摘要:

An overview of the method of surface differential reflectivity (SDR) for the study of semiconductor surfaces is presented. This includes the principles of the technique, the experimental apparatus, and some theoretical considerations concerning the connection of SDR data with the microscopic properties of the surface. Experimental results are also presented as an example of the application of this spectroscopy to the study of semiconductor surfaces.

ISSN:0734-2101    

DOI:10.1116/1.574154

出版商:American Vacuum Society    

年代:1987

数据来源: AIP

摘要:

A model is presented for calculating the film profiles of sputtered metal into axially symmetric contacts. The model assumes an isotropic source of metal vapor and considers the dynamic shadowing of deposition flux into the contact. Simulations from this model predict substantially worse step coverage than simulations from a two‐dimensional model but experimentally produced profiles have step coverages in between the two models.

ISSN:0734-2101    

DOI:10.1116/1.574155

出版商:American Vacuum Society    

年代:1987

数据来源: AIP

摘要:

Thin films of Ni covered with Au and supported on oxidized silicon wafers were deposited by thermal evaporation or electron beam evaporation. After heating in oxidizing environments from 250 to 400 °C, porosity was observed in the Au films. The pores were typically 2000 Å in diameter and ∼2 μm apart after heating for 1 h at 400 °C in oxygen. By considering models of grain boundary grooving, it has been shown that a porous, discontinuous thin Au film is thermodynamically stable.

ISSN:0734-2101    

DOI:10.1116/1.574156

出版商:American Vacuum Society    

年代:1987

数据来源: AIP