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Boron-suboxide films with hardness reaching 44 GPa, the highest record ever achieved, were synthesized. The films with such high hardness had an oxygen/boron atomic concentration ratio of 0.05 and a carbon concentration of about 20 at. %. They were deposited on silicon at 750 °C by simple sputtering. In the range of oxygen/boron ratio varying from 0.06 to 0.3, the film hardness and elastic modulus decreased monotonically. Unlike other hard film formation, argon ion bombardment of the film during film growth reduced the film hardness.

We used time-of-flight scattering and recoiling spectrometry to study the surface of a LiTaO3 (0001) single crystal as a function of temperature (22–200 °C). We found that the variations in surface voltage induced by pyroelectric changes of spontaneous polarization could be quantitatively estimated by computing the effects of surface voltage on the ion optics and scattering events, and measuring scattering and recoiling spectral peak shifts. Generally, when LiTaO3 (0001) in a steady state at room temperature was probed, its negative spontaneous polarization charge was compensated by an equivalent amount of positive surface charge and the surface voltage was virtually zero. Raising the sample temperature reduced the spontaneous polarization and indeed a rising positive surface voltage was recorded, which shows that the positive surface charge could not be drained out from the insulating surface instantaneously. However, above 160 °C, the surface voltage returned to around zero, which indicates the presence of a thermally induced surface charge compensation mechanism on LiTaO3 (0001) above 160 °C. Cooling the sample both closed this surface charge compensation channel and increased the negative spontaneous polarization charge. A rising negative surface voltage, which is a proper pyroelectric response, was experimentally recorded. However, the spectral changes in the cooling cycle were rather complex. First, peak shifts did not follow the theoretical pyroelectric changes, and second, unexpected additional peaks were observed. These spectral behaviors are attributed to the presence of enhanced ion induced electron and negative ion emission as additional surface charge compensation mechanisms which modified the pyroelectric changes of surface voltage on LiTaO3 (0001). In addition, these surface properties were found to be sensitive to surface treatments such as sputtering and proton exchange.We used time-of-flight scattering and recoiling spectrometry to study the surface of a LiTaO3 (0001) single crystal as a function of temperature (22–200 °C). We found that the variations in surface voltage induced by pyroelectric changes of spontaneous polarization could be quantitatively estimated by computing the effects of surface voltage on the ion optics and scattering events, and measuring scattering and recoiling spectral peak shifts. Generally, when LiTaO3 (0001) in a steady state at room temperature was probed, its negative spontaneous polarization charge was compensated by an equivalent amount of positive surface charge and the surface voltage was virtually zero. Raising the sample temperature reduced the spontaneous polarization and indeed a rising positive surface voltage was recorded, which shows that the positive surface charge could not be drained out from the insulating surface instantaneously. However, above 160 °C, the surface voltage returned to around zero, which indicates the presen...

The phase transformation of cubic boron nitride (c-BN) in the near-surface region of a c-BN (111) facet induced by argon-ion bombardment has been investigated by reflective electron energy-loss spectroscopy, with the objective of tracking possible growth mechanisms of c-BN in ion-assisted vapor deposition. For example, with an ion energy of 500 eV at a fluence of 5×1016 ions/cm2, 74% of c-BN were found transformed to h-BN and a-BN within the ion penetration depth of 11 A. Lowering the argon ion bombardment energy to 200 eV reduced the phase transformation depth to 7 A. A damage saturation was observed at a fluence of 6×1016 ions/cm2, at which up to 9% of the cubic phase were transformed. Similar measurements were performed at other ion energies. The present work gives a quantitative explanation of the difficulty in growing pure c-BN films with ion-assisted deposition and the presence of an upper-bound in ion energy above which the formation of phases other than the cubic phase dominate.

The deposition of cobalt-containing material from dicobalt octacarbonyl using a focused electron beam is reported. The material contains between 30% and 50% (atomic) cobalt, with the balance being carbon and oxygen, and comprises nanocrystalline metallic grains embedded in a carbonaceous matrix. Arches bridging two electrodes were fabricated to allow current–voltage (I–V) measurements to be conducted. The material resistivity decreases strongly with the deposition beam current, with values as low as 45 μΩ cm being attainable. Material growth by indirect irradiation is found to give rise to material of high resistivity and can result in highly resistive arches. At low temperatures, three distinctive conduction regimes are observed, with the I–V characteristics flattening out at the origin. At 20 K step-like features suggestive of Coulomb- blockade effects were observed. Magnetic force microscope (MFM) images of the material indicates that it is ferromagnetic in nature. The application of the technique and material to fabricate MFM tips is demonstrated. The use of selective material deposits as catalyst sites for the growth of carbon nanotubes is also demonstrated.

S+ ions with well-controlled kinetic energy were used to bombard n- and p-type GaAs (100) surfaces. 50 eV S+ bombardment formed a maximum of 1.5 monolayers of sulfide on a GaAs (100) surface and did not change the nonordered surface to an ordered surface. After the bombardment, the surface Fermi levels for both sulfur ion-bombarded n- and p-type samples were moved towards the midgap. After the samples were further annealed at 400 °C, the surface Fermi level of n- and p-type samples gave a separation larger than that of the samples after the UV/O3 and HF treatment. A sharp (1×1) low-energy electron diffraction pattern was observed and the sulfide coverage was about one monolayer. Under such well-controlled conditions, effective surface passivation by reducing surface states and formation of an ordered surface structure can be achieved.

A surface etching effect was observed using polysulfide solution for the passivation of III–V semiconductors. The etching rate was found to be 2 A/min on InP (100). The etching effect increased surface roughness, which enhanced the adsorption of adventitious hydrocarbons and water from the ambient. Such an etching effect was not observed on the samples treated by a gas-phase polysulfide treatment. The surfaces of these samples also showed less adventitious hydrocarbons and water after exposure to the ambient. The presence of sulfide on the surface reduced the sticking coefficient of the adventitious hydrocarbons and water.

Development of high quality ultrathin dielectric films of thickness less than 100 A has become an important research subject due to the scaling down of semiconductor devices. In the present study, samples with 20–100 A SiO2 on silicon were prepared by dry oxidation, and subsequently subjected to rapid thermal nitridation (RTN) using NH3 in the temperature range of 800–1200 °C. X-ray photoelectron spectroscopy and surface charge spectroscopy were applied to study the nitrogen distribution in the dielectric layers, the changes in the interface state density, Dit, and the dielectric breakdown field strength due to the nitrogen incorporation. It was found that nitrogen was mainly incorporated to the dielectric at the dielectric/Si interface without any consumption of silicon in the substrate during RTN. In the study of the electrical properties, we found that RTN led to a slight decrease in Dit and an increase in the breakdown field strength.

A special vacuum process has been developed for adding an OH functional group onto polymer surfaces with different reactivities. In this novel technique, polymer surfaces were exposed, in a vacuum chamber, to OH radicals generated by the dissociation of water vapor on hot rhenium wires. We found by x‐ray photoelectron spectroscopy and high resolution electron energy loss spectroscopy that about half a monolayer equivalent of C–OH groups could be generated on a relatively reactive polymer like polystyrene with a 10 s exposure at a water pressure of 1×10−3 Torr. However, under the same experimental conditions, the oxygen incorporation on more stable polymers was much lower; it was reduced by 90% on polyethylene and to practically zero on Teflon. For surface engineering of these stable polymers, thermionic electrons emitted from the hot filaments were used to facilitate electron impact ionization of some of the water vapor. Positive ions from the ionization region were then extracted and accelerated by an electrostatic field toward the polymer target which was separated from the ionization region by an adjustable distance about twice the gas‐phase collision mean‐free path. Although ion bombardment of the polymer surface was limited by the insulating property of the polymer, ion–molecule collisions in the gas phase were efficient with such a setup in generating energetic neutrals flying toward the polymer surface for the activation of the polymer. With an accelerating voltage of 50 V and a water pressure of 1×10−3 Torr (the collision mean‐free path being about 5 cm), about a 0.2 monolayer equivalent of COH was added to Teflon and polyethylene in 60 s.

The structural and chemical changes of the GaAs(110) surface induced by sequential processes of UV/O3 exposure, HF etching, and gas‐phase polysulfide passivation were investigated by x‐ray photoelectron spectroscopy (XPS), low‐energy electron diffraction (LEED), and thermal desorption. Prior to any annealing, no samples showed any LEED patterns, and XPS indicated the presence of both As–S and Ga–S bonds. When the polysulfide‐passivated surface was annealed to 400 °C, a sharp oblique LEED pattern started to emerge, which was accompanied by the desorption of S–As species. At the same time, XPS indicated that only a single type of sulfide (S–Ga) remained on the surface. Further annealing of the sample to 600 °C resulted in a complete removal of sulfur species from the surface and the appearance of a (2×1) LEED pattern. In contrast, no LEED pattern was observed from samples that had only been subjected to UV/O3 treatment and HF etching up to an anneal temperature of 600 °C, thus indicating the absence of any ...

Passivation of both cleaved GaAs(110) facets and wafers (both n and p types) was performed with different surface treatments including HF-etch of native oxide, passivation with an ammonium sulfide solution, passivation with hydrogen polysulfide, and passivation with a Si/S, Ge/S, or Si/Ge/S interface control layer. The interface state density was measured with capacitance–voltage (CV) measurements of metal–insulator–semiconductor capacitors fabricated on the passivated surfaces using remote plasma deposited silicon nitride as gate insulator. The interface structures of the capacitors were analyzed by x-ray absorption near-edge structure spectroscopy and x-ray photoemission spectroscopy. It was found that, while the passivation procedures with the sulfur compounds or a Si/S interface control layer did improve the CV data when compared with the HF oxide etch, the Si/Ge/S multilayer passivation technique led to the best CV results. By comparing the quasistatic and high frequency (1 MHz) CV data, we found that the minimum interface state density of the fabricated capacitors was about 10¹² eV⁻¹ cm⁻². The results were compared with those obtained from GaAs(100) and the difference was addressed with respect to the surface geometry and the electronic structures.

The effects of a gas‐phase polysulfide treatment on InP were studied by x‐ray absorption near‐edge structures (XANES) of both the sulfur L‐edge and K‐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 dependent K‐edge XANES. Both XPS and L‐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 in K‐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...

The analysis and removal of residual damage induced by reactive ion etching of silicon were studied with a new ultrashallow depth‐profiling technique of silicon. In this technique, which is known to give a depth resolution of better than 0.5 nm [Lau et al., Appl. Phys. Lett. 63, 78 (1993)], a few atomic layers of silicon were oxidized by an ultraviolet/ozone exposure at room temperature and subsequently removed by an HF wet etch. In the present study, the compositional changes during depth profiling and the amount of silicon removed per oxidation/etch cycle were estimated by x‐ray photoelectron spectroscopy. In addition, Rutherford backscattering spectroscopy was used to confirm the compositional changes and to measure defect depth distributions. Further, surface‐charge spectroscopy was applied to determine the minimum oxidation/etching required to completely remove Fermi‐level pinning associated with the residual damage. The results showed that these profiling and analysis techniques, when applied in a c...

Surface reactions on Si and SiO2 induced by CF+ and CF+2 from a mass‐separated ion‐beam system were studied with x‐ray photoelectron spectroscopy. The bombardment energies were varied from 100 to 2±0.6 eV. We found that the surface reactions induced by fluorocarbon molecular ion bombardment largely depended on the molecular identity of the ion species, its degree of molecular dissociation upon impact, and the reactivity of the substrate surface. Four examples are shown to illustrate this new approach in altering reaction pathways. (1) CF+ bombardment at 2 eV: This led to molecular adsorption on both Si and SiO2 and to SiFx formation on Si but little reaction with SiO2. (2) CF+/20 eV: This led to a higher probability of molecular dissociation upon impact and thereby opened the channel for CF disproportionation. The energy carried by the fragment was sufficiently high that the reaction channels with SiO2 was also opened. (3) CF+/100 eV: This resulted in efficient molecular dissociation and incorporation of ...

The interfacial reactions between ion beam deposited diamondlike carbon (DLC) films on ZnS were studied by x‐ray photoelectron spectroscopy. The DLC films were deposited by pure C+ ion bombardment. The results were also compared with those obtained from ion beam deposited DLC on Ge. It was found that the films (2–20 nm thick) deposited with a pure C+ beam in the energy range of 20–300 eV on these two substrates always showed two carbon phases with a C 1 s binding energy difference of about 0.8 eV. The low binding energy carbon phase showed an average location among about 30 samples at about 284.4±0.2 eV whereas the high binding energy carbon phase showed it at 285.5±0.2 eV. Although carbon in a carbide form typically has C 1s binding energy about 1 eV lower than that in graphite (284.7 eV), the observed difference of 0.9 eV in binding energies of the two carbon phases was not a consequence of one phase being metal carbide. Instead, the presence of these two phases appears to be characteristic of the DLC f...

The fabrication of p–n junctions in silicon with junction depths of a few nanometers and the determination of the potential distribution and junction depth of such a specimen with a depth resolution of better than 0.5 nm were performed. The ultrashallow p–n junctions were formed by bombarding hydrogen‐passivated n‐Si(100) with BF2+ of less than 500 eV. After being annealed at 500 °C in vacuum for an hour, the sample surfaces were treated with a HF solution for the reduction of surface states in the band gap of silicon prior to junction characterization. With hydrogen passivation, the separation between the Fermi level and the valence band maximum of the semiconductor surface, EFs, an energy which is governed by the doing type and net carrier concentration, was measured with x‐ray photoelectron spectroscopy. The sample was then subjected to ozone oxidation at room temperature for 20 min, a procedure which reproducibly consumes 0.5 nm of silicon. The oxide was then removed by a HF solution to reveal a new h...

Chemical modifications in the surface of gallium arsenide bombarded with low energy, 3–300 eV CF+ ions have been investigated using x‐ray photoelectron spectroscopy (XPS). The effect of temperature on the modified surface was studied by annealing in a vacuum of 1×10−6 Pa prior to further XPS analysis. It was found that CF+ ion bombardment deposited an overlayer containing both carbon and fluorine on the GaAs surface. At 3 eV CF+ ion exposures, the overlayer consists primarily of CF and CC bonds whereas at experimental energies greater than the dissociation energy of the CF bond, there are appreciable amounts of CF2 and CF3 indicated. The GaAs surface itself is modified slightly, to include some gallium and arsenic fluorides, and perhaps some carbides as well. The levels of these components are limited, however, by the presence of the CF overlayer which upon forming encapsulates the GaAs surface, shielding it from subsequent CF+ bombardment. The overlayer also retains gallium and arsenic fluorides in the G...

Releasing the Fermi‐level pinning of InP by gas phase polysulfide exposure has recently been demonstrated by surface charge spectroscopy [Lau et al., Surf. Sci. 271, 579 (1992)]. The present article reports a study of capacitance–voltage (C–V) measurements on metal–insulator–semiconductor (MIS) diodes fabricated using a process which includes this polysulfide passivation. The effectiveness of this passivation technique in reducing interface trap densities (Dit) was confirmed. The optimized MIS fabrication procedure involved (a) surface cleaning and polysulfide exposure; (b) immediate deposition of silicon nitride by remote plasma chemical vapor deposition (RPCVD); and (c) deposition of aluminum and annealing at 500 °C for 15 min in forming gas. The C–V results gave a Dit of 5×1010 cm−2 eV−1 via the Terman analysis and 5×1011 cm2 eV−1 via the high–low frequency method. The MIS properties were unchanged after a two months air exposure and a one week 110 °C heating in air. It was also found that the replacement of aluminum with Ti/Pt/Au, and of RPCVD with plasma enhanced chemical vapor deposition all led to higher Dit values.

Surface modifications of silicon by exposure to a mass‐separated, reactive ion beam of CF+ were studied by x‐ray photoelectron spectroscopy. The effects of ion kinetic energy were characterized in terms of the various surface chemical states induced by the bombardment. The results showed that with an ion kinetic energy of 2 eV, which was much lower than the C–F bond energy of about 5 eV, molecular adsorption took place. At a bombardment energy of 10 eV, dissociative chemisorption was observed but the reaction was confined to the top surface with disproportionation of CF as the main route and little fluorination of silicon. With an ion energy of 100 eV, the atomic fragments generated by the CF dissociation possessed enough energy to penetrate below the silicon surface. It was found that silicon carbide and fluorosilyl species comprised the modified surface region and that fluorine atoms were situated closer to the surface than the carbon atoms of the carbide. Fluorocarbon species were minor surface reactio...

The surface reactions induced by BF+ and BF+2 bombardment of gold at 10–250 eV were studied with a mass‐separated low energy ion beam system. The energy distributions of dissociative ion fragments and survival molecular ions were measured by low energy ion scattering with a scattering angle of 90° and polar incident angle of 45°. The results suggest that neutralization of BF+ and BF+2 via resonance charge transfer, Auger neutralization, and collisional charge exchange all contribute to the reduction of the parent ion intensity. In the study of dissociative scattering, the observed onset values of 35 eV for BF+ dissociation and 20 eV for BF+2 dissociation indicate that dissociation occurs mainly via vibrational excitation at impulsive collision with the surface. In addition, secondary ion mass spectrometry, secondary neutral mass spectrometry, and x‐ray photoelectron spectroscopy analyses of gold surfaces bombarded with BF+ and BF+2 show that the dissociation also leads to the accumulation of boron and bor...

Indium nitride deposition on Si(100) using modulated In+ and N+2 has been carried out in a mass‐separated low energy ion beam system. In+ and N+2 were generated in a Colutron ion source loaded with pure indium and fed with nitrogen, and were focused into a Wien filter. The mass analyzer was switched manually or by a computer for modulating the selection of In+ and N+2. After passing through the Wien filter, the selected ion beam was focused to the target chamber and was decelerated by a five‐element deceleration lens in front of the target. In situ x‐ray photoelectron spectroscopy (XPS) was used for film characterization. The spectral data confirmed the formation of InNx but the x value was less than unity for films prepared using ion energies of 5–100 eV and In/N dose ratios of 2–6. For example, the film prepared with an In/N ratio of 1/6 at a beam energy of 5 eV showed a composition of InN0.4. It was found that argon ion sputtering of this film at 1 keV and at a polar angle of 80° further depleted the n...

The surface of gallium arsenide has been bombarded with low energy fluorine ions in order to study their role in modifying the surface during a CHF3 reactive ion etch of oxide overlayers on GaAs. Compositional changes caused by the bombardment of GaAs with ions ranging in energy from 10 to 300 eV have been investigated using x‐ray photoelectron spectroscopy. Depth profiling information was obtained using angle‐resolved photoemission measurements. Annealing in vacuum of 1 × 10−6 Pa was investigated as a means of returning the bombarded surface to its original condition. It was found that F+ ion bombardment incorporated fluorine into the surface of GaAs and depleted it of arsenic by forming gallium fluoride and apparently releasing volatile arsenic fluoride. Monitoring the Ga 3d peak revealed that three gallium fluoride phases corresponding to GaF, GaF2, and GaF3 were formed. The extent of fluorine incorporation and arsenic depletion were dependent upon incident F+ ion energy, reaching a maximum at low incident ion energies around 50 eV. At higher ion energies the amounts of GaF2 and GaF3 decreased more than that of GaF. Post‐bombardment annealing in vacuum was successful in removing the residual fluoride phases at temperatures below 305 °C. GaF3 was the first component to desorb and GaF the last. The resulting GaAs surface, however, was still gallium rich, likely due to the presence of some residual gallium oxide.

To simulate the low energy ion bombardment that occurs in reactive ion etching (RIE) using alkanes, GaAs and InP were exposed to 20, 100, and 500 eV carbon ions, using a mass‐separated carbon ion beam in an ultrahigh vacuum chamber. The InP sample structure consisted of a 40 A ultrathin, epitaxial InP layer on InGaAs. The changes induced by ion bombardment and the effects of subsequent damage‐removal treatments were determined by in situ polar‐angle dependent x‐ray photoelectron spectroscopy. Initially, carbon ion irradiation caused minor sputtering of the semiconductors and preferential removal of the group V constituents, with concurrent formation of carbon‐semiconductor phases. The depth of these phases and the extent of the damage increased with increasing bombardment energy. An amorphous carbon residue formed after further bombardment. Several damage removal techniques were applied to the carbon bombarded surfaces. It was found that heating was ineffective in annealing the damage, although surface Fermi level movements were observed. Ozone oxidation did not remove the residual carbon efficiently, yet the underlying semiconductor components were readily oxidized. Hydrogen ion bombardment was effective in removing the carbon bombardment induced damage. The implications of these results for alkane based RIE processes are discussed.

Surface chemistry, and surface Fermi level (EFs) changes on InP, as a result of exposure to several sulfur compounds, and of subsequent heating were studied by x‐ray photoelectron spectroscopy. It was found that after p‐InP samples were exposed to a mixture of hydrogen sulfide and polysulfide, heating at 200–300 °C induced a strong type‐inversion of the semiconductor surface. However, subsequent heating at 400 °C returned EFs towards the valence band maximum (VBM). From many repeated experiments, EFs was found to be changed in the range of 0.5–1.2 eV (referenced to VBM). Further studies on exposure to other sulfur compounds including hydrogen sulfide, sulfur, and sulfur dioxide showed that the large range of EFs movement correlated only with polysulfide. The overall spectral results suggest that adsorption of hydrogen polysulfide reduced surface states in the band gap of InP and led to the formation of donor states near the conduction band minimum of InP upon heating at 200–300 °C. Further heating at 400 ...

The effects of hydrofluoric acid etching of SiO2/Si on surface band bending of p‐ and n‐Si, and the thermal stability of such effects were studied by x‐ray photoelectron spectroscopy and Raman spectroscopy. It was found that near flat band surfaces could be prepared on p‐ and n‐Si by HF etching. However, a significant increase of surface band bending was found when p‐Si was treated with an HF concentration of higher than 10%. Raman spectroscopy confirmed that excessive hydrogen incorporation deactivated the boron‐dopant in Si by forming an H–B–Si complex. Nevertheless, the boron dopant could be reactivated by annealing at a temperature as low as 120 °C.

The use of an ultrathin amorphous silicon layer at the interface between silicon nitride and InP has been studied. The objective was to reduce the interface state density of the dielectric‐semiconductor structure. Amorphous silicon and silicon nitride were deposited sequentially in the same remote plasma chemical vapor deposition chamber with a base pressure in ultrahigh vacuum. Less than 2 nm of amorphous silicon was deposited on InP by decomposing silane in a remote plasma. Three different plasmas, argon, helium, and hydrogen were tried. Silicon nitride was deposited by reacting silane with atomic nitrogen from a remote nitrogen plasma. Most of the processing steps were monitored by x‐ray photoelectron spectroscopy (XPS) with sample transfer in ultrahigh vacuum. The degree of Fermi level pinning of InP at the resultant interface was studied by surface charge spectroscopy (SCS). It was found that the deposition of amorphous silicon in the nanometer thickness range could be readily controlled. The amount ...

The effects of various sulfide treatments on n‐ and p‐InP and the stability of the sulfide‐passivated surfaces have been studied by x‐ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). When the sulfide treatments were performed at room temperature, a reduction of donor‐type surface states was induced as indicated by a decrease of surface band bending on p‐InP. However, such surface passivation deteriorated when annealed at 200–300 °C in vacuum, and a strong type inversion with band bending reaching 1.3 eV was observed on p‐InP. XPS data from the annealed samples suggest that the presence of polysulfides plays an important role in the cause of the observed strong type inversion. However, SIMS analysis of the type‐inverted samples indicated that the sulfur concentration at a depth of 7.5 nm from the surface was less than the SIMS detection limit for sulfur in InP (5×1016 atoms/cm3). In addition, XPS studies of the type‐inverted samples showed that reversal of the type inversion...

A deceleration lens system for low energy ion beam transport applications in the region of 10–200 eV has been designed, constructed and experimentally characterized. In this ion beam system, the target is required to be in an almost field‐free region at the exit of the lens to allow for maximum target maneuverability. The lens design was optimized using the simulation data obtained with chden, a computer program for calculating ion trajectories with space‐charge included. The design chosen in this work was a five‐electrode lens which can be operated in either a simplified two‐electrode deceleration mode or, when the best system performance is required, in a five‐electrode decelerator‐focusing mode. The performance of the lens was experimentally evaluated by using a 3 keV pure argon ion beam with a beam size of about 1 mm2 and beam current of about 10μA which was generated by a modified Colutron Ion Gun Model G‐2 unit. The lens decelerated the incident beam to 10–200 eV and transported it to either a Farad...

X‐ray photoelectron spectroscopy (XPS) has been used to study the native oxide structure and surface Fermi level of GaAs exposed to ultraviolet light (UV)/ozone, as well as to monitor changes that occur during thermal desorption of the surface oxide. The XPS results confirm that the surface oxide consists of a mixture of gallium and arsenic oxide phases which desorb at two different temperature ranges: desorption of arsenic oxide phases and oxygen transfer from arsenic to gallium occur at 250–500 °C; and desorption of gallium oxide phases occurs at 550–600 °C. In addition, we found that the surface Fermi level of GaAs below the UV/ozone formed oxide was always at about 0.8 eV from the valence‐ band maximum (VBM) for n‐type substrates and 0.5 eV for p‐type substrates. Similar results were found for wet chemically treated and then air exposed GaAs surfaces. However, the surface Fermi levels of both n‐ and p‐type substrates, during the desorption of arsenic oxide in the temperature range of 250–500 °C, moved...

Ion bombardment during deposition can significantly modify the film properties. In the partially ionized beam deposition, ions derived from the depositing material, i.e., the self‐ions, are used during deposition. Cu films were deposited on SiO2 substrates at room temperature using 1% Cu self‐ions with an energy ranging between 0–4 keV. We studied the microstructures of the Cu films using x‐ray diffraction and transmission electron microscopy, measured the impurity level inside the films using secondary ion mass spectrometry, and performed the resistivity measurements using a four point probe. The results indicate that there is an optimum ion energy around 2 keV at which, the integrated x‐ray intensity ratio I(111)/I(200) reaches its maximum value indicating a strong 〈111〉 texture, while the impurity concentration and resisitivity are minimum. The correlation between the structural, compositional and electrical properties are discussed in the framework of Mayadas and Shatzkets’s theory of grain boundary r...

A method was proposed and examined to deposit thick cubic boron nitride (cBN)-rich layer of good adhesion to silicon substrate. The method combined (i) the insertion of a thick sp2 buffer layer, and (ii) the use of an appropriate assist ion beam energy for the growth of the cBN-rich top layer. The sp2-bonded boron nitride buffer layer was deposited under irradiation of ions with energies in the range of 200–360 eV. The buffer layer was found to contain curled graphitic basal planes, and so was supposed to be relatively deformable, and facilitate the relaxation of stresses in the cBN-rich top layer. The ion assist introduced during the growth of the cBN-rich layer was supposed to both create and annihilate defects, and so resulted in the generation and relaxation of internal stresses. Results showed that the insertion of a 492 nm sp2 buffer layer, and the use of a beam energy of 450 eV for assisting the growth of the top layer can produce a 643-nm-thick cBN-rich top layer with satisfactory adhesion, a high cBN content of 87 vol %, a hardness of 57 GPa, and an elastic modulus of 612 GPa.

The formation of sacrificial oxides on GaAs surfaces has become the normal procedure in the preparation of in situ cleaned substrates for molecular‐beam epitaxial growth. In this paper we show that sacrificial oxides can be formed on InP by a UV/ozone treatment, yielding more controlled and reproducible properties than thermal and air formed oxides. Results from x‐ray photoelectron spectroscopy studies on acid/DI water/air and UV/ozone treatments are compared. It is shown that thermal desorption of the former leaves residues containing carbon which can seriously degrade epitaxial growth, whereas UV/ozone formed sacrificial oxides could be removed at 494 °C leaving atomically clean, stoichiometric surfaces.

In0.53Ga0.47As layers grown on InP substrates by metalorganic chemical vapor deposition were oxide ‘‘capped’’ using a UV ozone treatment. Oxide removal was accomplished by thermal desorption in vacuum and by remote hydrogen plasma treatments carried out in reaction chambers attached to a high spectral resolution x‐ray photoelectron spectrometer (XPS). The XPS spectral results showed the oxide layer to be composed of a mixture of oxides. Subsequent desorption occurred over a range of temperatures. Desorption of As and In oxides, oxygen transfer from oxidized to nonoxidized sites and the formation of the suboxides occurred as intermediate stages. Complete removal of all oxides was observed at a temperature above the decomposition temperature of the In0.53Ga0.47As. The use of atomic H, generated in a remote plasma system, to enhance oxide removal was found to be a more effective procedure; the complete removal of all oxides was achieved at a substrate temperature of 192 °C. The resulting surface composition ...

The interfacial reactions between metals and the anodic oxide of mercury cadmium telluride (MCT) have been studied by polar‐angle‐dependent x‐ray photoelectron spectroscopy. It was found that the deposition of thin metal films (

A remote plasma enhanced chemical vapor deposition reactor has been constructed which can be directly attached to a high spectral resolution x‐ray photoelectron spectroscopy (XPS) system, thereby allowing the application of thin dielectric films and subsequent study of the interface by XPS without the need to resort to sputter‐profile techniques. This apparatus has been used to study the deposition of silicon nitride (≤5 nm thick) on various n‐ and p‐type surfaces of InP and GaAs. The effect of the remote plasma alone has also been investigated. The studies focus on the chemical structure of the near surface region and the surface Fermi‐level (FL) position of the substrate using XPS. It was seen that thin, uniform films of silicon nitride could be obtained with ≤1% oxygen content. The spectra of the underlying substrate were seen to be very similar to that of the clean surface, thereby indicating a sharp and clean interface region. There were no ‘‘(III–V)–N’’ bonds apparent, as was the case with the inter...

An x‐ray photoelectron spectrometer coupled with an ultrahigh vacuum specimen preparation chamber was used to study the formation and removal of surface oxides on n‐ and p‐type InP surfaces. Multiple oxide phases were formed by surface oxidation with molecular oxygen or UV/ozone. On n‐type InP, the surface Fermi level initially moved down to 0.3 eV below the conduction band minimum (CBM) with low oxygen exposures but finally pinned at 0.1 eV with exposures higher than 1012 L. On p‐type InP, the Fermi level moved monotonically towards the CBM and eventually pinned at 0.6 eV for an oxygen exposure higher than 1012 L. Although more indium and phosphorus oxides were formed upon prolonged air or ozone exposure, these final pinning positions were the same as for pure dry oxygen. The surface oxides could be desorbed at 458 °C resulting in a reduced surface band bending of