James R Engstrom

• PhD
• Professor (Full) at Cornell University

We have examined the atomic layer deposition (ALD) of Al2O3 using a nonpyrophoric precursor, which possesses only Al–N bonds and no Al–C bonds: Al(N(CH3)2)2(–N(C2H5)–C2H4–N(C2H5)2), which we refer to as bis-dimethylamino-diamino-aluminum (BDMADA-Al). We employed a quartz crystal microbalance (QCM) to monitor ALD in situ and in real time, and the de...

We have examined the nucleation and growth of WSe2 thin films in ultrahigh vacuum on highly oriented pyrolytic graphite (HOPG) using in situ real-time x-ray fluorescence (XRF), and ex situ x-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy. We employed W(CO)6 as the W source delivered via...

In this work, we investigate the atomic layer deposition (ALD) of ZrO2 thin films on Cu and SiO2 substrates, using Zr[N(C2H5CH3)]4 as the thin-film precursor, and H2O or O2 as the coreactants. Here, we introduce 3-hexyne as a coadsorbate molecule during the thin-film precursor half-cycle and examine its effect on the selectivity of growth. We find...

Density functional theory (DFT) is used to better understand the oxidation of Pd metal using vacuum ultraviolet (VUV) light co-exposed with O2, which is known to produce O and O3. The oxidation of Pd metal arising from O, O2, and O3 is assessed on bare Pd, Pd with a 0.25 monolayer of adsorbed atomic O, and Pd with increasing O incorporation into th...

Low-temperature, plasma-free atomic layer etching of Pd⁰ is explored. A vacuum ultra-violet light source (115 nm < λ < 400 nm) is used in conjunction with a controlled O2 gas exposure to produce PdOx at 100 °C. The amount of PdOx that forms is dependent on the duration of co-exposure of O2 at 1 Torr and vacuum ultra-violet irradiation. A minimum co...

In this work, we have explored the use of a third species during chemical vapor deposition (CVD) to direct thin-film growth to occur exclusively on one surface in the presence of another. Using a combination of density functional theory (DFT) calculations and experiments, including in situ surface analysis, we have examined the use of 4-octyne as a...

The authors report the design and characterization of a microreactor probe that enables gas-phase reactions such as atomic layer deposition (ALD) at low-to-medium vacuum, which is coupled directly to an ultrahigh vacuum (UHV) analysis chamber for subsequent in situ surface characterization without an air break. Avoiding this air break is critical t...

We have examined the effect of growth rate on the growth mode of thin films of tetracene on SiO2 at a substrate temperature of 0 °C. For a preponderance of conditions examined here, only the thin-film phase is formed. From a combination of in situ real-time synchrotron X-ray scattering and ex situ atomic force microscopy, we have observed a transit...

We have examined the effect of growth rate on the evolution of two polymorphs of thin films of tetracene on SiO2 using synchrotron X-ray radiation and molecular beam techniques. Ex situ X-ray reflectivity shows that tetracene forms two phases on SiO2: a thin-film phase and a bulk phase. We have used in situ, real-time grazing incidence diffraction...

Thin film processing technologies that promise atomic and molecular scale control have received increasing interest in the past several years, as traditional methods for fabrication begin to reach their fundamental limits. Many of these technologies involve at their heart phenomena occurring at or near surfaces, including adsorption, gas-surface re...

We have examined the growth of bilayers and superlattices of pentacene and perylene derivatives (PTCDI-Cn) using in situ real time X-ray synchrotron radiation techniques and ex situ atomic force microscopy. We find that the growth of PTCDI-Cn layers on 1 monolayer (ML) of pentacene is initially 2D layer-by-layer (LbL), eventually transitioning to a...

Surface states of colloidal nanocrystals are typically created when organic surfactants are removed. We report a chemical process that reduces surface traps and tunes the inter-particle coupling in PbS nanocrystal thin films after the surfactant ligands have been stripped off. This process produces PbS/PbI2 core/shell nanocrystal thin films via a c...

The authors have examined the effect of two molecules that form self-assembled monolayers (SAMs) on the subsequent growth of TaNx by atomic layer deposition (ALD) on two substrate surfaces, SiO2 and Cu. The SAMs that the authors have investigated include two vapor phase deposited, fluorinated alkyl silanes: Cl3Si(CH2)2(CF2)5CF3 (FOTS) and (C2H5O)3S...

The authors have examined the nucleation of diindenoperylene (DIP) on SiO2 employing primarily atomic force microscopy and focusing on the effect of incident kinetic energy employing both thermal and supersonic sources. For all incident kinetic energies examined (Ei = 0.09–11.3 eV), the nucleation of DIP is homogeneous and the dependence of the max...

The authors have examined ultrathin (≤10 Å) tantalum nitride (TaNx) thin films deposited by atomic layer deposition (ALD) on three surfaces relevant to interconnect layers in microelectronic devices: thermally grown SiO2; a Cu thin film grown by physical vapor deposition, and a carbon-doped SiO2 porous low-κ thin film. The authors have employed ex...

We have examined the initial stages of atomic layer deposition (ALD) of TaNx on SiO2, a porous low-κ SiO2-based material, and both of these substrates modified by a branched interfacial organic layer, using in situ X-ray photoelectron spectroscopy (XPS) as the primary analytical method. The interfacial organic layer examined was poly(ethylene imine...

Molecular imaging of a select few chemical species with sulfur-containing head groups adsorbed on a Au(111) surface using ultrahigh-vacuum scanning tunneling microscopy(UHV-STM) is reviewed and our recent work is reported. Self assembled monolayers (SAMs) of n-alkanethiols on Au(111) are known to give various surface structures. Prevailing surface...

We have examined the thin film growth of pentacene on SiO2 and on three different polymeric dielectrics using in situ synchrotron X-ray scattering and ex situ atomic force microscopy (AFM). The polymeric dielectrics investigated spanned the range from a low surface energy hydrophobic surface (polystyrene, PS) to a high surface energy hydrophilic su...

The atomic layer deposition (ALD) of a series of inorganic thin films on an interfacial organic layer has been examined, focusing on the existence of a delay in thin film nucleation and its dependence on the chemistry of each ALD reaction. The inorganic thin films examined were Al2O3, HfO2, Ta2O5, and TaNx, while the organic layer was a thin (∼5 Å...

Over the past several years significant advances have been made concerning our understanding of the growth of crystalline small molecule organic thin films consisting of a single component. An important challenge in organic electronics, photonics and photovoltaics is to develop and improve methods to integrate both p-type and n-type small molecule...

We have examined the nucleation, growth, and dynamics of the adsorption of N,N′-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C13) on SiO2 surfaces modified by self-assembled monolayers (SAMs) and on a predeposited monolayer of pentacene using in situ synchrotron X-ray scattering and ex situ atomic force microscopy. From real-time X-ra...

We have examined the initial stages of growth of a crystalline small molecule organic thin film, diindenoperylene (DIP), on SiO(2) surfaces terminated with a series of self-assembled monolayers (SAMs). In this study we make use of supersonic molecular beam techniques to vary the incident kinetic energy of the DIP molecules, and we use in situ, real...

Self-assembled monolayers (SAMs) of either ferrocenecarboxylic acid or 5-(4-Carboxyphenyl)-10,15,20-triphenyl-porphyrin-Co(II) (CoP) with a high- dielectric were integrated into the Flash memory gate stack. The molecular reduction-oxidation (redox) states are used as charge storage nodes to reduce charging energy and memory window variations. Throu...

Synchrotron-based x-ray reflectivity is increasingly employed as an \textit{in situ} probe of surface morphology during thin film growth, but complete interpretation of the results requires modeling the growth process. Many models have been developed and employed for this purpose, yet no detailed, comparative studies of their scope and accuracy exi...

The assembly of colloidal nanocrystals (NCs) into superstructures with long-range translational and orientational order is sensitive to the molecular interactions between ligands bound to the NC surface. We illustrate how ligand coverage on colloidal PbS NCs can be exploited as a tunable parameter to direct the self-assembly of superlattices with p...

Three-dimensional Kinetic Monte Carlo simulations were used to model the deposition of a hyperthermal molecular beam at varying angles of incidence. The simulations incorporate incident atom-substrate interactions, many layer growth, and attempt to mimic deposition and growth of Si on a Si(100) substrate. At high angles of incidence, the formation...

The reaction of Si2H6 with the Si(100) surface has been examined via supersonic molecular beam scattering techniques. The effects of incident translational energy, incident angle, mean vibrational energy and surface temperature have been considered explicitly. It is found that the reaction probability is most sensitive tothe incident translational...

We have carried out a series of experiments aimed at producing arrays of mesas on both Si(001) and Si(111) which are free from atomic steps. These are of interest in CMOS technology and for quantum well structures. They also provide interesting substrates for fundamental surface science experiments. In previous work we have created atomically flat...

We have examined the nucleation and growth of perfluoropentacene (PFP) on SiO2 and on a variety of surfaces possessing different terminating self-assembled-monolayers (SAMs) using in situ synchrotron X-ray scattering and ex situ atomic force microscopy. The SAMs ranged from very low surface energy hydrophobic surfaces (perfluorooctyltrichlorosilane...

The interfaces between inorganic and organic materials are important to a wide variety of technologies. A significant challenge concerns the formation of these interfaces when the inorganic layer must be grown on a pre-existing organic layer. In this review the authors focus on fundamental aspects of inorganic-organic interface formation using tran...

The three-dimensional reconstruction of a porous low-dielectric constant film (κ = 2.5), resolving pores as small as 1 nm, was achieved using annular dark-field scanning transmission electron tomography, enabling quantitative measurements of the pore morphologies and size distribution. Most large pores were elliptical. Together with log-normal pore...

We demonstrate that small-molecule organic thin films of pentacene deposited from thermal and supersonic molecular beam sources can undergo significant reorganization under vacuum or in N2 atmosphere, beginning immediately after deposition of thin films onto SiO2 gate dielectric treated with hexamethyldisilazane (HMDS) and fluorinated octyltrichlor...

We have examined the dynamics of the adsorption of pentacene molecules on SiO2 and on a pentacene surface at room temperature using a combination of supersonic molecular beam techniques, atomic force microscopy, and atomic-scale molecular dynamics simulations. For incident kinetic energies, Ei = 1.5−6.7 eV, and angles of incidence, θi = 0–75°, we f...

Top-contact organic thin-film transistors (OTFTs) of pentacene have been fabricated on bare SiO2 and SiO2 modified with hexamethyldisilazane (HMDS) and octadecyltrichlorosilane (OTS). The pentacene films were deposited from a supersonic molecular beam source with kinetic energy of incident molecules ranging from1.5 to6.7eV. The field-effect mobilit...

We have examined the dynamics of adsorption of diindenoperylene (DIP) on SiO(2) and SiO(2) modified with an interfacial organic layer using in situ real time synchrotron x-ray scattering, focusing on the effects of coverage. On both surfaces we observe a substantial increase in the probability of adsorption with increasing coverage, which is most d...

A self-assembled monolayer of 1-octanethiol was prepared on a Au(111) surface via liquid-phase adsorption. An investigation of the surface using ultrahigh-vacuum scanning tunneling microscopy revealed a striped phase of the octanethiol molecules under the conditions examined. This phase resembles the well-known "pinstripe" structure of alkanethiols...

We have investigated the growth of hyperbranched polyglycidol films, and their subsequent reaction with a transition metal coordination complex, pentakis(dimethylamido)tantalum, Ta[N(CH 3) 2] 5 using ellipsometry, contact angle measurements, atomic force microscopy and X-ray photoelectron spectroscopy (XPS). Up to thicknesses of approximately 150 A...

Thin film growth of pentacene on SiO2 using a supersonic source has been investigated with in situ real time synchrotron x-ray scattering and ex situ atomic force microscopy, focusing on the effects of incident kinetic energy Ei and growth rate GR on the evolution of surface roughness and the crystalline structure of the thin films. For the conditi...

We have investigated the growth of first generation branched polyamidoamine dendrons on silicon dioxide as a way to tailor and control the subsequent chemisorption of transition metal coordination complexes. Beginning with straight-chain alkyl, amine-terminated self-assembled monolayers as anchors, we find that the efficiency of the dendritic branc...

Atomic layer deposition (ALD) of titanium nitride, TiN, from the reaction of Ti[N(CH3)2]4 and NH3 on silicon dioxide, and silicon dioxide modified by interfacial organic layers with different structures (straight-chain vs branched) and functional terminations (−OH, −NH2, and −CH3), has been investigated employing molecular beam techniques, atomic f...

Atomic layer deposition (ALD) of titanium nitride (TiN) on silicon dioxide and silicon dioxide modified by self-assembled monolayers (SAMs) with different structures and functional terminations has been investigated employing molecular beam techniques. On the –CH3 terminated SAMs, growth is significantly attenuated over that observed on clean SiO2,...

The reaction of a transition metal coordination complex, Ti[N(CH3)2]4, with self-assembled monolayers (SAMs) possessing–OH, –NH2, and –CH3 terminations has been examined using supersonic molecular beam techniques. The emphasis here is on how the reaction probability varies with incident kinetic energy (Ei=0.4–2.07eV) and angle of incidence (θi=0°–6...

Nucleation and growth of pentacene on silicon dioxide surfaces modified with hexamethyldisilazane, HN[Si(CH3)3]2, has been examined using supersonic molecular beam techniques and atomic force microscopy. Similar to growth on clean SiO2 surfaces, the rate of deposition at a fixed incident flux decreases with increasing kinetic energy of incident pen...

An atomistic mechanism has been derived for the initial stages of the adsorption reaction for metal-nitride atomic layer deposition (ALD) from alkylamido organometallic precursors of Ti and Zr on alkyltrichorosilane-based self-assembled monolayers (SAMs). The effect of altering the terminal functional group on the SAM (including -OH, -NH2, -SH, and...

We have investigated the reaction of tetrakis(dimethylamido)titanium, Ti[N(CH(3))(2)](4), with N-isopropyl-N-[4-(thien-3-ylethynyl) phenyl] amine and N-isopropyl-N-(4-{[4-(thien-3-ylethynyl) phenyl]ethynyl}phenyl) amine self-assembled monolayers (SAMs), on polycrystalline Au substrates. The structure of the SAMs themselves has also been investigate...

A surface modification strategy for the use of giant magnetoresistive materials in the detection of protein-protein interactions is developed. This modification strategy is based on silanization of semiconductive materials. A native silicon nitride surface was treated with concentrated hydrofluoric acid to improve surface homogeneity. Nano-strip wa...

The nucleation of pentacene on silicon dioxide, incident at hyperthermal energies, has been investigated with atomic force microscopy. The incident kinetic energy of the pentacene molecules strongly influences the process of adsorption—the adsorption probability decreases with increasing incident energy, indicative of trapping-mediated adsorption....

The reactions of tetrakis(dimethylamido)titanium, Ti[N(CH(3))(2)](4), with alkyltrichlorosilane self-assembled monolayers (SAMs) terminated by -OH, -NH(2), and -CH(3) groups have been investigated with X-ray photoelectron spectroscopy (XPS). For comparison, a chemically oxidized Si surface, which serves as the starting point for formation of the SA...

Toluene, a volatile organic compound (VOC), was removed from water using a stripping process in both a traditional randomly packed tower and a microfabricated stripping column (MFSC). The MFSC, fabricated using standard Si processing techniques, resulted in overall capacity coefficients, Kxa, nearly an order of magnitude greater than the packed tow...

The growth and nucleation of silicon thin films on silicate glasses of variable composition were analyzed using supersonic gas source molecular beam deposition. The growth of silicon thin films was investigated using scanning electron microscopy. It was observed that the incubation time of the growth was varied with substrate composition, and was i...

Supersonic molecular beam techniques have been used to study the nucleation of Si and Si1-xGex thin films on Si and SiO2 surfaces, where Si2H6 and GeH4 have been used as sources. A particular emphasis of this study has been an examination of the effects of a coincident flux of atomic hydrogen. The time associated with formation of stable islands of...

Controlling film quality and modeling the growth of organic/inorganic interfaces comprises unique challenges in thin film science, especially when trying to understand the fundamental limits of charge transport in such interfaces. AFM and synchrotron X-ray experiments demonstrate that previous dynamic scaling theories can be used to predict nucleat...

Using plane wave pseudopotential density functional theory calculations we have identified for the first time precursor states for hydrogen atom chemisorption on the Si(100)-(2×1) surface. These states exist above clean, partially, and fully monohydride-adsorbed surface dimers. In all three cases the dimer bond is broken in the trapped state. A stu...

The nucleation of copper on TiN and SiO2 surfaces has been investigated using a collimated molecular beam of hexafluroacetylacetonate copper(I) trimethylvinylsilane in ultrahigh vacuum. The Cu thin film precursor was delivered using a bubbler with H2 as the carrier gas and the substrate temperature was varied from 150 to 260 °C. Ex situ analysis of...

X-ray photoelectron spectroscopy (XPS) and low-energy ion scattering spectrometry (LEISS) have been employed to study the kinetics of etching by atomic hydrogen of Ge overlayers on Si(100). The coverage of Ge as deduced by both XPS and LEISS decreases dramatically after exposure to atomic hydrogen, and the decrease is exponential with exposure time...

We present here a low-temperature (T-s< 630 degreesC) process for the selective epitaxial growth of Si that employs atomic hydrogen. Modulation of both the substrate temperature and the flux of atomic hydrogen gives alternating growth and suppression/etching cycles, resulting in a significant increase in selectivity. Epitaxial thin-film quality is...

We describe a method for producing arrays of atomically flat mesa structures on Si(111) through the deposition of Si on a lithographically patterned substrate in the temperature range 750–850 °C. The Si source was a supersonic beam of Si2H6. With an appropriate choice of substrate temperature and deposition rate, the atomic steps initially present...

The interaction of atomic hydrogen with both the clean Si(1 0 0) surface, and this same surface under conditions leading to steady-state epitaxial growth of Si from the reaction of disilane, Si2H6, has been examined. Reflectance anisotropy spectroscopy has been employed to measure the hydrogen adatom coverage on vicinal Si(1 0 0) surfaces as a func...

In many respects materials science and related fields are driven by the discovery process. Combinatorial chemistry, the technique of creating vast numbers of compounds by reacting a set of components in all possible combinations at once, holds tremendous promise for greatly accelerating materials discovery and optimization processes. This approach,...

Recent experimental results concerning Ge segregation in Si _1-x Ge _x epitaxial thin films deposited on Si(100) substrates using Si ₂ H ₆ and GeH ₄ cannot be accounted for by a simple two-site model involving surface and bulk states. This is due to Ge enrichment in the subsurface layers. H...

A new technique to deposit silicon thin film employing supersonic beams is examined. Our previous studies involved both experimental and numerical approaches, in which the thin films were deposited at a high growth rate but over relatively small areas. The current studies are focused on the process scale-up by using multiple supersonic jets. Three...

Epitaxial silicon thin films were deposited on Si(100) substrates at variable angles of incidence using well-collimated supersonic molecular beams of disilane, Si2H6. The resulting thin-film surface topology has been examined using atomic force microscopy. Rough surface morphology is observed as the beam angle of incidence is increased above ∼60°....

Supersonic molecular beams have been investigated as alternative sources for thin film deposition employing a custom designed ultrahigh vacuum reactor. Molecular beam flux produced in this reactor has been measured as a function of gas flow rate, gas composition, and nozzle temperature. An efficient method to measure kinetics of thin film depositio...

Low-energy ion scattering spectrometry (LEISS) and x-ray photoelectron spectroscopy (XPS) have been employed to quantify in situ the near-surface composition of strained Si1−xGex epitaxial thin films grown on Si(100) substrates using GeH4 and Si2H6 as sources. The use of LEISS reveals the Ge concentration in essentially the first monolayer, whereas...

Supersonic molecular beam techniques have been employed to examine the dissociative adsorption of GeH4 and Si2H6 on strained Si1−xGex (0≤x≤1) epitaxial overlayers deposited on Si(100). Low-energy ion scattering spectrometry (LEISS) has been utilized to quantify in situ the topmost Ge surface composition of the Si1−xGex films. Through the measuremen...

Kinetic and dynamic information from semiconductor surfaces is of great importance in the understanding of growth processes in molecular beam epitaxy. Surface related information, such as coverage and composition, is often measured with techniques such as temperature programmed desorption under conditions away from those encountered in a realistic...

Two- and three-dimensional kinetic Monte Carlo simulations were used to model the deposition of a hyperthermal molecular beam at varying angles of incidence. The simulations incorporate realistic deposition and diffusional moves, and feature many-layer growth for large systems containing up to 80 000 atoms. Kinetic Monte Carlo simulations for the t...

Deposition of epitaxial silicon thin films through the seeding of silicon hydride molecules in a supersonic beam of light carrier gas is modeled using the direct simulation Monte Carlo technique. In this process, a hyperthermal collimated beam is formed by rapid expansion through a nozzle orifice and then refined through a skimmer. The fundamental...

Supersonic molecular beam techniques have been employed to examine the dissociative adsorption of GeH4 and Ge2H6 on the Si(100) and Si(111) surfaces. At sufficiently high incident kinetic energies (⩾ 1 eV), both species on both surfaces react via a direct dissociation mechanism. At sufficiently low incident kinetic energies (⩽ 0.6 eV) and substrate...

The reaction probabilities of GeH4 and Ge2H6 on the Ge(100) and Ge(111) surfaces have been measured as a function of substrate temperature, incident kinetic energy, and angle of incidence employing supersonic molecular beam scattering techniques. At sufficiently large incident kinetic energies (Ei≳1 eV) both GeH4 and Ge2H6 react by direct dissociat...

The dissociative chemisorption of phosphine, PH3, on the Si(100) surface has been examined with supersonic molecular beam scattering techniques. The effect of phosphorus adatoms, P(a), formed by the dissociative chemisorption of PH3, on the reaction of SiH4 and Si2H6 with Si(100) has also been characterized. All reactions have been examined at subs...

The reactions of silane, SiH4, disilane, Si2H6, and phosphine, PH3, on single crystalline Si(100) and Si(111) surfaces, and methylsilane, SiH3CH3, on a beta-SiC surface have been examined employing supersonic molecular beam scattering. The emphasis here is not on any one experimental result, but rather on the specific experimental approaches adopte...

The dissociative chemisorption of phosphine, PH3, on the Si(111)-(7 × 7) surface has been examined employing supersonic molecular beam techniques. The initial probability of reaction, SR,0, has been found to be sensitive to substrate temperature, Ts, where SR,0 increases sharply by approximately a factor of 4–5 as Ts is increased above 800°C, which...

The thermal and plasma‐assisted nitridation of GaAs(100) using NH 3 has been examined employing x‐ray diffraction, Auger electron spectroscopy, and atomic force microscopy to characterize the nitrided films. All thermally nitrided films were composed of a mixture of hexagonal and cubic GaN, whereas the addition of plasma excitation produced films p...

The reaction of disilane, Si2H6, with the Si(100) and Si(111) surfaces has been examined with supersonic molecular beam scattering techniques. The emphasis has been on elucidating the reaction mechanism operative under conditions leading to steady‐state Si epitaxial growth. Two reaction mechanisms have been identified: (i) complete pyrolysis to for...

The effect of PH3on the dissociative chemisorption of SiH4 and Si2H6 on the Si(100) surface has been investigated with supersonic molecular beam techniques. Adsorbed phosphorus atoms, formed as a result of the reaction of PH3on the Si surface, inhibit the dissociative chemisorption of both SiH4 and Si2H6 through a short‐range steric mechanism. The...

We present a review of our recent work concerning supersonic molecular beam scattering of thin film precursors from the Si(100) and Si(111) surfaces. Both SiH4 and Si2H6 exhibit translationally activated dissociation channels at sufficiently high incident kinetic energies, (E┴) 0.5 eV. the dominant variables under our reaction conditions are the in...

The reaction of SiH4 on clean Si(100) and Si(111) has been investigated employing supersonic molecular beam scattering techniques. The probability of dissociative adsorption, SR, of SiH4 on both surfaces depends strongly on incident kinetic energy, increasing nearly exponentially with increasing energy. On clean Si(100), SR exhibits a weak dependen...

Recent experimental results concerning reactive scattering in the hyperthermal kinetic energy regime can be described by energy scaling relationships Ei cosn θi, where n

The reactions of Si 2 H 6 with the (100) and (111) surfaces of silicon have been investigated employing supersonic molecular beam scattering techniques. Incident translational energy has been found to influence strongly the probability of dissociative adsorption (S R ) on both surfaces. The reaction on the Si(111) surface is distinct from that obse...

The reaction of Si2H6 with the Si(100) surface has been examined via supersonic molecular beam scattering techniques. It is found that the reaction probability is most sensitive to the incident translational energy, varying nearly linearly with increasing energy for 〈Etr〉≳1 eV. The effect of incident angle θi is described by a model that accounts e...

The reactions of atomic oxygen with the (100) and (111) surfaces of silicon have been investigated by employing supersonic molecular beam techniques, X-ray photoelectron spectroscopy (XPS), and low-energy ion scattering spectroscopy (ISS). Atomic oxygen adsorbs with unit probability on the clean silicon surface, independent of substrate temperature...

The reactions of atomic oxygen with the (100) and (111) surfaces of silicon have been investigated by employing supersonic molecular beam techniques and X-ray photoelectron spectroscopy. The kinetics and mechanism of the active oxidation reaction, i.e., Ox(g) + Si(s) → SiO(g) where x = 1 or 2, has been evaluated by employing modulated molecular bea...

The reaction of atomic oxygen with the Si(100) surface has been examined by employing supersonic beam techniques. Atomic oxygen adsorbs with unit probability on the clean Si(100) surface. The rate of oxidation decreases rapidly with increasing coverage up to ~3-4 monolayers, followed by a regime that exhibits a weaker dependence on coverage. At sur...

The hydrogenation, isomerization, and hydrogenolysis of cyclopropane, methylcyclopropane, and propylene have been investigated on the (111) and (110)-(1Ã2) single-crystalline surfaces of iridium at reactant partial pressures from 0.4 to 10 Torr of hydrocarbon (P{sub HC}) and between 20 and 500 Torr of hydrogen (P{sub Hâ}) and at surface temperature...

The effect of coincident ion bombardment on the oxidation of Si (100) by atomic oxygen has been examined under ultrahigh vacuum conditions by employing molecular beam techniques and x‐ray photoelectron spectroscopy. Ion bombardment leads to a significant enhancement in the rate of oxidation. By modulating both the oxygen and ion (Ar⁺ ) f...

The adsorption and reaction of atomic oxygen on the Si(100) surface has been examined by employing supersonic beam techniques, x‐ray photoelectron spectroscopy, and mass spectrometry. Atomic oxygen adsorbs with a unit probability of adsorption on the clean Si(100) surface, independent of incident translational energy, incident angle, and surface te...

The adsorption and reaction of both molecular and atomic flourine with the Si(100) surface has been examined under ultraligh vacuum conditions with supersonic molecular beam techniques, X-ray photoelectron spectroscopy (XPS), quadrupole mass spectrometry and low-energy ion scattering spectroscopy. Molecular flourine adsorbs dissociatively on the cl...

The hydrogenolysis of ethane, propane, n-butane, and neopentane has been investigated on the (111) and (110)-(1Ã2) single-crystalline surfaces of iridium at reactant partial pressures between 0.2 and 5.0 Torr of hydrocarbon and between 20 and 500 Torr of hydrogen and for surface temperatures from 400 to 700 K. A coupled high-pressure reactor-ultrah...

Surface temperature modulation has been employed to investigate the adsorption, desorption and oxidation of CO on the Pt(110)-(1 × 2) surface. Examination of the adsorption-desorption equilibrium allows a determination of the kinetic parameters describing the desorption reaction. In the limit of zero coverage, the activation energy of desorption is...

The thermal decomposition of silicon-fluoride adlayers, produced by exposing a clean Si(100) surface to a molecular beam of fluorine, have been investigated under ultrahigh-vacuum conditions with x-ray photoelectron spectroscopy and mass spectrometry. The only gas phase reaction products detected from temperature-programmed desorption are SiF2 and...

The adsorption and reaction of atomic oxygen on the Si(100) surface has been examined by employing supersonic beam techniques, X-ray photoelectron spectroscopy and mass spectrometry. Atomic oxygen adsorbs with a unit probability of adsorption on the clean Si(100) surface. The probability of adsorption decreases monotonically with increasing coverag...

The theoretical formulation of a frequency response technique, based on surface temperature modulation, for the study of surface reaction dynamics is described in detail. The formalism is developed for analyzing adsorption, desorption, and both unimolecular and bimolecular surface reactions. The evaluation of the activation barriers for the element...