摘要:

The thermal and electron‐induced decomposition of Fomblin–Zdol lubricant on a rigid magnetic disk with a hard carbon overcoat are studied by temperature‐programmed reaction/desorption spectroscopy and electron stimulated desorption. The thermal spectroscopy shows two desorption features peaked at 640 and 700 K resulting from decomposition of the Fomblin–Zdol molecules. The threshold temperature for dissociation of the Fomblin–Zdol molecule is at 500–550 K in accordance with the known thermal stability of the free molecule. HF originating from thermal reactions with either surface OH or surface CH groups is a prominent desorption product. Electron impact also causes Fomblin–Zdol dissociation. Two efficient mechanisms for electron impact dissociation have been resolved separately above and below the ionization threshold of ∼14 eV. The low‐energy process is likely due to the formation of negative ions followed by dissociation (dissociative electron attachment) and has a cross section of ∼2×10−16cm2. These results show that Fomblin–Zdol as a lubricant on a magnetic disk is inherently unstable thermally and in the presence of triboelectrons.

ISSN:0734-2101    

DOI:10.1116/1.579393

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Layers of lithium fluoride (LiF), ∼10 nm thick, were field desorbed from iridium substrates at temperatures between 25 and 600 °C. The electric field was increased until desorption of the salt layer occurred. Combined mass spectroscopy and field desorption microscopy characterized the desorption process. During desorption, ions of the form (LiF)n⋅Li+,n=1–4 are created. The field strength required for desorption is higher at lower temperatures and decreases as the temperature of the substrate is increased. Evidence for a piecewise removal of the LiF layer is presented. For thick salt layers, Li+ions are frequently detected. An ion production mechanism based on ionic conduction of a salt layer in a high electric field is presented.

ISSN:0734-2101    

DOI:10.1116/1.579394

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

The thermal reactions of CF3I, CF3CH2I, and C2F4are studied by temperature‐programmed reaction/desorption (TPR/D) on a Si(100) surface. CF3I, CF3CH2I dissociate on the surface, whereas C2F4adsorbs reversibly, without dissociation. Dissociation of the iodine‐containing molecules is probably initiated by the cleavage of the relatively weak C–I bonds. In the case of CF3I, the C–I bond dissociation generates I(a) and CF3(a). I(a) desorbs as atomic I. CF3(a) dissociates in sequence, producing gas phase SiF2and SiF4and a carbon deposit on the surface. In the case of CF3CH2I, the C–I bond dissociation generates I(a) and CF3CH2(a). CF3CH2(a) undergoes β–F elimination to form gas phase CF2CH2as well as further decomposition on the surface. At higher temperatures H2, I, HI, and SiF2desorb and carbon deposits on the surface.

ISSN:0734-2101    

DOI:10.1116/1.579395

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

The surface free energies of diamond crystals under different chemical vapor deposition conditions have been comprehensively calculated. The calculations are based on a model where a fraction of carbon dangling bonds on the growth surface are saturated by hydrogen atoms. The results show that the surface free energies increase with the increasing substrate temperature or the decreasing hydrocarbon concentration in hydrogen and intersect each other at a critical point when the surface coverage fraction is equal to 0.83 monolayers. The results are excellent in theoretically interpretating the changes of predominant facets in the surface morphology from {100} to {111} with the increasing substrate temperature or the decreasing hydrocarbon concentration in hydrogen.

ISSN:0734-2101    

DOI:10.1116/1.579396

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Small quantities of adsorbed C have been deposited on Pd(112) by the dissociative adsorption of C2H4. It is demonstrated that although Auger electron spectroscopy is insensitive to the presence of this C(ads), temperature programmed desorption (TPD) can be used to determine the cleanliness of the surface. TPD spectra following the 300 K adsorption of15NO on C‐covered Pd(112) indicate that reactive chemistry occurs during heating, as evidenced by the production of high temperature15N2(≊590 K) and CO (≊520 K) thermal desorption features. The results of this study are used to formulate an improved method for the removal of C from Pd surfaces in ultrahigh vacuum.

ISSN:0734-2101    

DOI:10.1116/1.579397

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Positive and negative direct current (dc) bias effects were investigated for the synthesis of hydrogenated amorphous carbon films in radio frequency plasma chemical vapor deposition at 0.025 Torr and 200 °C. The applied bias ranged from +250 to −500 V. Both the positive and negative dc bias effects are discussed on the basis of surface and cross‐sectional morphology by scanning electron microscopy, deposition rate, threshold energy for photoelectron emission, contact angle, and adhesive strength of these films. For a negative bias, the surface of the film is very flat. The surface of the film deposited with no bias is somewhat pebbly while that of the film deposited with a positive bias is very rough and shows the presence of pores in the cross section. A negative bias substantially increases the deposition rate, refractive index, wettability, and adhesive strength. With no bias (ground potential), as compared to with a positive bias, there is a little increase in the wettability and adhesive force. The no bias case did not affect the properties arising from structural change, such as refractive index (density) and threshold energy for photoelectron emission (incorporated hydrogen). A positive bias did not affect these physical properties of the hydrogenated amorphous carbon films. These positive, negative, and no bias effects depend on the kinds of collision species and their collision energy against the substrate in the radio frequency plasma according to the additional bias conditions.

ISSN:0734-2101    

DOI:10.1116/1.579398

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

The interface formation of Cr/NH3/GaAs(100) and its temperature dependence using synchrotron radiation photoemission and resonance photoemission spectroscopies have been investigated. We observed that atT=90 K the initial deposition of Cr stimulated nitridation of the GaAs substrate and subsequent interface reaction was characterized by Cr‐induced substrate disruption. Annealing of the thus formed interface to room temperature and above caused further Cr–GaAs reaction. The metallicity of the Cr overlayer was examined using constant initial‐state spectroscopy (CIS) of Cr 3dwithEi=1.7 eV below the Fermi level. The CIS spectra showed a maximum at the photon energyhν=50.0 eV followed by a second broad maximum centered athν=56–58 eV depending on the stage of the interface formation. As the nominal Cr coverage increases from 1 to 10 Å, the valence band photoemission spectra show a shift of the Cr 3dband toward the Fermi level. At the same time, the second maximum in CIS gradually dominates over the first, suggesting the evolution of the Cr overlayer to a more metallic state. The sensitivity of the second maximum in its peak position and intensity to the density of states near the Fermi level indicates that this maximum likely results from many body electron interactions. The results show that CIS can provide valuable information about the transition of a thin overlayer to a metallic state.

ISSN:0734-2101    

DOI:10.1116/1.579399

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Ar+sputter‐induced microprotrusions on monocrystalline InP at −100 °C, room temperature, and 100 °C were investigated by scanning and transmission electron microscopy. On a target cooled down to −100 °C, the protrusions were of dual structure, having an amorphous layer thickly covering the monocrystalline core. At room temperature, the protrusions that formed involved randomly oriented domains at the tip area, suggesting a recrystallization process occurring under ion impact. Heating the target to 100 °C resulted in a dramatic change in protrusion morphology and structure. Typically, the protrusions on the heated target could be classified as fibrous or whiskerlike protrusions or short ones topped with metallic crystallites. Crystal growth processes thus appeared to be involved in sputtering at 100 °C.

ISSN:0734-2101    

DOI:10.1116/1.579400

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Measurements of local order are demonstrated in Sn‐containing alloys and epitaxial monolayer thickness films by analysis of extended‐edge energy loss fine structure (EXELFS) data obtained by reflection electron energy loss spectrometry (REELS). These measurements of short‐range order provide a complement to the chemical information obtained with REELS and long‐range order obtained using reflection high energy electron diffraction. The results suggest that EXELFS measurements are practical for samples mounted on the growth manipulator in a molecular beam epitaxy chamber. Advantages and limitations of reflection EXELFS are discussed.

ISSN:0734-2101    

DOI:10.1116/1.579401

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

The adsorption/desorption kinetics of TiCl4on polycrystalline TiSi2have been measured quantitatively by temperature‐programmed desorption in order to better understand the chemical vapor deposition of the silicide from TiCl4and SiH4. For small exposures, only SiCl2desorbs near 1150 K. The kinetics are second order with respect to surface chlorine, and the desorption activation energyEdis 85±4 kcal/mol. As this state approaches saturation, SiCl2desorbs from a second state near 700 K. The kinetics are also second order, but desorption occurs through a continuum of energetic pathways peaking at 57 kcal/mol. As this state saturates, a third desorption peak consisting of SiCl4appears near 500 K. The kinetics are first order with respect to surface chlorine and also comprise a distribution of energetic pathways, which peak at 33 kcal/mol. Coadsorption studies with SiH4were also performed. Surface chlorine appears to bond to Si, not Ti, on the surface. These kinetics are utilized to predictively model the chemical vapor deposition of TiSi2thin films.

ISSN:0734-2101    

DOI:10.1116/1.579402

出版商:American Vacuum Society    

年代:1995

数据来源: AIP