In this paper, we review and highlight the central role that infrared spectroscopy has played in elucidating the microscopic details of the bonding and exfoliation processes and we introduce a novel technique for imaging and measuring strain with submicron resolution. The mechanism for chemical bond formation between two interfaces is derived from monitoring the chemical evolution of interfacial species as a function of annealing. The mechanism for silicon shearing upon Himplantation/annealing is understood as an evolution of H-passivated point defects into H-stabilized internal surfaces, together with H2 formation. The nucleation and propagation of microbubbles that form prior to exfoliation is imaged with x-rays and a detailed strain map in the vicinity of bubbles just prior to exfoliation can be made.

Recent work has demonstrated that the process of silicon thin-film separation by hydrogen implantation, as well as the more basic phenomenon of surface blistering, can occur at a much lower total dose when H and He are co-implanted than when H is implanted alone (1). Building on that work, this paper investigates the role of implantation damage in this process by separating the contributions of gas pressure from those of damage. Three different experiments using co-implantation were designed. In the first of these experiments, H and He implants were spatially separated thereby separating the damage from each implant. The second experiment involved co-implantation of H and He at a temperature of 77 K to retain a larger amount of damage for the same gas dose. In the third experiment, Li was co-implanted with H, to create additional damage without introducing additional gas. These experiments together show that increasing the implantation damage itself hampers the formation of surface blisters, and that the increased efficiency observed for He co-implantation with H is due to the supplementary source of gas provided by the He (1).

We present the results of a combined theoretical and experimental study of the growth of extended surface vibrational modes during the initial oxidation of Si(100)-(2x1). Controlled incorporation of oxygen into the first two layers of the silicon surface is achieved via sequential water (H2O) exposures and stepwise annealing in ultrahigh vacuum. Transmission infrared spectroscopy is used to monitor the transition from vibrational modes characteristic of isolated Si-O structures, so-called silicon epoxides, to extended modes with the character of transverse optical and longitudinal optical phonons in an extended SiO2 film. Quantum chemical calculations on two-dimer silicon clusters identify these modes as arising predominantly from coupling between species on adjacent dimer units, consistent with the thermodynamic driving force for local oxygen agglomeration. The vibrational signature of this surface is proposed to offer a link between well-characterized local surface Si-O structures and the extended SiOx film that exists between Si(100) and SiO2 after thermal oxidation of silicon. (C) 2003 American Institute of Physics.

Adhesion at asperity-asperity contacts plays a critical role in tribology. Studies of nanoparticle films with atomic force microscope (AFM) tips provide a means of probing adhesion at such nanoscale contacts. Here, the molecular details of adhesion at silica nanoparticle (similar to50 nm diameter) surfaces under various aqueous solution conditions have been investigated using a combination of atomic force microscopy and ab initio quantum chemical calculations. The adhesion between surface bound silica particles and the AFM tip mimics the colloidal interactions between silica particles in solution and depends on the intrinsic surface composition under the varying solution conditions. Depending on pH, the measured adhesion between the surfaces is a mixture of hydrogen bonding (dropSi-(OHHO)-H-...-Sidrop), anionic hydrogen bonding (dropSi=(OH)(2)-...HO-Sidrop) and formal covalent bonding, via formation of siloxane (dropSi-O-Sidrop). In order to decouple the number density and energetics of each type of interaction within the nanospheric contacts formed between the surfaces, the adhesion measurements by AFM have been referenced to detailed ab initio quantum chemical calculations of the relevant interactions. This combined approach affords the description of the adhesion with molecular definition and the statistical distribution of interactions between particles can be evaluated.

Due to the extreme dimensional scaling required by Moore's law, Si device technology is increasingly subject to the limitations imposed by the intrinsic physics and chemistry of surfaces and interfaces. In this review we outline ways in which fundamental surface science has contributed an understanding to the microelectronics community and discuss areas where surface science may impact future development. We focus on the example of silicon dioxide (SiO2) on silicon, since this interface lies at the heart of modern transistor technology and has therefore received a great deal of attention in recent years. We highlight a number of experimental and theoretical approaches that have elucidated the fundamental phenomena associated with the formation and evolution of this critical technological interface, revealing the remarkable interdependence of science and technology that now characterizes this rapidly evolving industry.

The surface of SiO2 in contact with a liquid has been studied in situ by Fourier transform infrared spectroscopy, electrochemistry and ab initio quantum chemical calculations. Experimental issues arising from the cell designed have been addressed, notably the influence of the medium above the SiO2 film on the line shape of the Si–O vibrations. Using electrical potential control of the surface with electrochemistry, the hydrated states of the SiO2 surface have been identified, featuring a neutral SiOH species and pentavalent Si(OH)OH− anionic centers.

The average size of the silver nanoparticles, prepared by the method of Korgel and co-workers [10], is approximately 5 nm. A solution containing 0.3 g of toluene and 0.5 mg of PS, with approximate molecular weight of 900 000, was then added to 0.5 mg of these silver nanocrystals in a vial. The corresponding volume ratio Ag/PS was estimated to be 0.1. The solution was sonicated for 20 min to evenly disperse the particles. Approximately 0.5 mL of the resulting solution was then cast on water, contained in a 3 inch petri dish. Evaporation of solvent was slowed by completely covering the dish. Under this condition, toluene molecules escaped from the tiny gap between the dish and its cover. After 1 h, the toluene evaporation was complete and a shining, wrinkle-free, purple colored nanocomposite film formed on the water surface. When the film preparation was accelerated by uncovering the dish, the toluene evaporation was non-uniform and wrinkles developed.

Over the past two decades, infrared absorption spectroscopy (IRAS) has emerged as a preeminent technique for studying semiconductor surface and interface passivation [1]. For example, it has played a central role in identifying the nature of the HF induced passivation by hydrogen of Si surfaces [2–6] and, more recently, in describing the microscopic mechanism of surface oxidation [7–9]. In such studies not only can the nature of the surface termination (SiHx,(x=1–3), or SiOx,(x=0–2)) be determined, but the orientation of the various species can also be quantified, thus providing structural as well as chemical information. At present, IRAS exhibits sufficiently high sensitivity that it is possible to detect as little as 1% of a hydrogen monolayer. This effectively allows the characterization of minority surface species (steps, defects) as well as of the majority surface termination. In addition, the high spectral resolution afforded by IRAS can be utilized to distinguish subtle differences in chemical environment (due to the presence of dangling bonds, for example) and to unravel complex dynamical effects, such as coupling between isolated surface modes and the substrate phonons or electrons.

An atomic scale model of thermal oxidation of Si(100) has been developed based on a kinetic Monte Carlo approach. This method makes it possible to analyze the effects of elementary mechanistic steps of oxidation on macroscopic surfaces. The initial thermal decomposition of chemisorbed hydroxyl groups resulting from water adsorption on Si(100)-(2×1) is investigated by utilizing extensive IR data and ab initio calculations.

Spectroscopy was performed along three distinct crystallographic axes of a high refractive index contrast photonic crystal and the spectra were compared with theoretical calculations. Deep dips were observed in the experimental spectra at 2.1 and 3.2 μm and predicted by calculations. The photonic crystal was prepared through melt-imbibing of selenium into a self-assembled face-centered-cubic colloidal crystal template.

The nature of the silicon oxide transition region in the vicinity of the Si/SiO2 interface is probed by infrared and x-ray photoelectron spectroscopies. The layer-by-layer composition of the interface is evaluated by uniformly thinning thermal oxide films from 31 Å down to 6 Å. We find that the thickness dependence of the frequencies of the transverse optical and longitudinal optical phonons of the oxide film cannot be reconciled by consideration of simple homogeneous processes such as image charge effects or stress near the interface. Rather, by applying the Bruggeman effective medium approximation, we show that film inhomogeneity in the form of substoichiometric silicon oxide species accounts for the observed spectral changes as the interface is approached. The presence of such substoichiometric oxide species is supported by the thickness dependence of the integrated Si suboxide signal in companion x-ray photoelectron spectra.

Surface infrared spectroscopy and density functional cluster calculations are used to study the thermal and atomic hydrogen-induced decomposition of water molecules on the clean Si(100)-(2×1) surface. We report the first observation of the Si–H bending modes associated with the initial insertion of oxygen into the dimer and backbonds of a silicon dimer. We find that, while one and two oxygen-containing dimers are formed almost simultaneously during the thermal decomposition of water on this surface, atomic H can be used to drive the preferential formation of the singly oxidized dimer. This work highlights the sensitivity of Si–H bending modes to the details of local chemical structure in an inhomogeneous system, suggesting that the combined experimental and theoretical approach demonstrated herein may be extremely useful in studying even more complex systems such as the hydrogenation of defects in SiO2 films.

In this paper, we review the pivotal role that defects (in particular vacancy structures) play in driving the H-induced exfoliation of Si. We highlight the central role that infrared spectroscopy has played in delineating the microscopic details of the exfoliation process. We show that when the results of such spectroscopic studies are combined with those obtained using a variety of other experimental probes as well as ab initio quantum chemical cluster calculations, an unambiguous mechanistic picture emerges. Specifically we find that H-terminated vacancy structures drive the formation of internal surfaces into cracks where H2 is then evolved, resulting in the build-up of sufficient internal pressure to cause lift-off of the overlying Si. The role of coimplantation of He is also discussed.

An experimental method, based on infrared absorption spectroscopy, has been developed to study ultra-thin passivating layers on semiconductor surfaces. To characterize the interface of thin films, a two-pronged approach has been used: thinning of the film to highlight the properties of the interfacial layer and growth of the passivating film in a controlled fashion. In the latter approach IR spectroscopy is used at each growth step to probe the atoms both above and below the semiconductor surface. This approach is illustrated for the prototypical case of H2O reaction on Si(100)-(2 x 1), a system that provides a means to grow thin oxide films while following in great detail how oxygen is inserted into silicon and ultimately forms amorphous SiO2.

Recent developments in the major experimental vibrational-spectroscopic techniques (i.e. infrared absorption, Raman scattering, high resolution electron loss, helium atom scattering and sum frequency generation) are reviewed and illustrated with selected results. Particular emphasis is given to two important topics which have attracted much attention in recent years: (i) the complex surface reactions taking place on technologically relevant surfaces and interfaces, and (ii) vibrational dynamics with emphasis on energy dissipation at surfaces.

We have used infrared absorption spectroscopy and x-ray photoelectron spectroscopy to study the thermal evolution (under ultrahigh vacuum conditions) of ultrathin silicon oxide films grown in acid solutions (HCl, HNO3, and H2SO4). We find that adsorbed hydrocarbon contaminants dissociate and become chemically incorporated into the thin oxide as additional silicon oxide, carbide, hydride, and hydroxyl species. These species significantly influence the thermal evolution of the oxide films and persist up to the SiO desorption temperature (850–1000 °C) so that, once formed, these defects will be necessarily present in the final device structure.