Single crystal silicon wafers were treated by direct oxynitridation using electron cyclotron resonance (ECR) and radio-frequency (rf) plasma with separate N2 and O2 gas sources. Fabricated layers were characterized by ex situ spectroscopic ellipsometry (SE), Auger electron spectroscopy (AES), and atomic force microscopy (AFM).

The thickness and nitride/oxide ratio of silicon oxynitride layers were found to be dependent on the main process variables, namely gas pressure, bias voltage, and N2/O2 flow rate ratio. It was also observed that ECR/rf plasma is more efficient for the formation of layers with higher nitrogen content at relatively low pressure (≤ 200 mTorr) and bias voltage (−40 V) when compared to that of rf plasma alone. SE modeling provided good fitting to experimental data, while AES and AFM analyses supported SE results. The effects of fabrication conditions on the thickness and composition of the layers will be presented.

The Kardar-Parisi-Zhang (KPZ) surface roughening model was proposed nearly fifteen years ago. Although there have been many theoretical studies, there are very few experimental examples of thin film evolution obeying the KPZ equation. We discuss the physical basis of the KPZ equation and suggest possible reasons for the departure from KPZ behavior that is usually observed in surface growth/etching processes. Particularly, we construct a non-local, KPZ-like growth model that takes into account the effect of surface re-emission and show that, for certain limits, our model reduces to the KPZ model. We also discuss various experimental results in the context of known roughening models, including our model.

Instability in the morphology of atomic steps is predicted for certain growth conditions [1]. To test and extend this prediction, various atomic step geometries were prepared on ultra-flat Si(111) substrates. Atomic steps were observed using an in situ scanning electron microscope. For specific growth conditions and certain step arrangements, unstable growth was observed. The stability of step flow growth depends, in part, on the flux arriving at the surface. In contrast to the theoretical prediction, in this more general situation, the same type of instability can also be observed in sublimation. For both growth and sublimation, the terrace widths adjacent to a step determine whether that step will undergo stable or unstable step flow. The mechanism by which the step spacing controls the morphology is described. Although only the Si(111) surface was observed, it is predicted that the same step instability should be present on many surfaces.

We develop a rate-equation model for surface growth in ion beam assisted deposition. In terms of the rate coefficients the model describes how island detachment and breakup, adatom diffusion and interlayer transitions of adatoms affect the growth. We identify parameter values corresponding to different modes of growth and discuss our results and ways to improve the model.

We have performed computer simulation studies on the 22×√3 surface reconstruction of Au(111). This reconstruction involves a uniaxial contraction of the top monolayer corresponding to a surface strain of about 4.3% and has been observed to be the stable structure for clean surfaces at low temperatures. A continuum model yields a stability criterion that depends on the knowledge of a small number of measurable physical quantities: surface stress f, surface free energy γ, lattice parameter a0 and shear modulus µ. The simulations using EAM potentials accurately reproduce many observed features of the reconstruction and tend to support the continuum model and the resulting stability criterion.

Here we report our investigations on the initial stages of Cu(OO1) oxidation in dry and moist atmosphere using in situ ultra high vacuum (UHV) transmission electron microscopy (TEM), atomic force microscopy (AFM) and scanning electron microscopy (SEM). Cu20 islands were observed to grow 3-dimensionally into the Cu film as seen through the above mentioned techniques. Further, we discuss our interpretation of the experimental observations that presence of water vapor in the oxidizing atmosphere retards the rate of Cu oxidation and Cu20 shows surprising reduction when exposed to water vapor.

Thin films of gold (Au) were grown on single crystal germanium (Ge) or silicon (Si) substrates using physical vapor deposition (PVD). The resulting microstructure was that of a mazed bicrystal in which two equivalent grain orientations, related to each other by a 90° rotation, are arranged in a morphology of irregularly shaped, convoluted grains. Quantitative morphological analysis showed a strong dependence of grain shape on size, with larger grains being more convoluted and smaller grains more compact. The evolution of grain size, anisotropy and shape during heating in the temperature range from 300-340 °C was studied by in-situ transmission electron microscopy (TEM).

GaN is a wide gap semiconductor which is now used to produce blue and green light emitting diodes, blue laser diodes and which has numerous other potential applications, like high frequency HEMT transistors, UV sensors, etc. A complicated two step process, using a low temperature buffer layer, subsequently annealed and followed by the deposition of the monocrystalline semiconductor was developed, and due to the excellent results obtained following this method, a rush towards applications resulted. There is now a need to investigate in more detail the growth mechanisms, and the influence of the growth parameters, in order to ensure a better reproducibility of the results. In this paper, we report an investigation of the growth mechanisms and the influence of the growth parameters using in-situ reflectance experiments. The reflectance measurements allow us to follow the growth rates, and the changes in the surface morphology (transitions between islands growth and 2D growth). Additional exsitu measurements (AFM ) were performed at different stages of the growth process to ensure additional information. As a result, we demonstrate that the recrystallization of the low temperature buffer layer is a critical step, which is drastically influenced by the composition of the annealing atmosphere (amount of ammonia present in the gas phase), while the deposition temperature and buffer thickness have a moderate effect. We will discuss here the growth mechanisms which may be involved to explain such a behavior.

We report an in-situ study of the MBE growth of Cu films on hydrogen-terminated Si (001) and (7×7) reconstructed Si(111) substrates. Using correlated RHEED and STM data, we find a dramatic smoothing of epitaxial Cu(001) surfaces by annealing the as- grown films in the 120-160oC temperature range and somewhat less so for the Cu (111) films. Our measurements reveal a lower activation energy (0.40 ± 0.04 eV) for inter- terrace mass transport in Cu(001) than for Cu(111) (1.10 ± 0.03 eV) the former possibly influenced by the presence of hydrogen. Scaling analysis of the subsequent Cu growth on the annealed smooth surfaces yields a coarsening exponent of 1/4 for the (001) oriented films while this exponent is 1/3 for the (111) films, providing for the first time experimental data for the same system in these two orientations.

Orthorhombic β-FeSi2 thin-films were prepared on Si(100) and Si(111) substrates by a pulsed laser deposition method. When the substrate temperature was 500°C, β-FeSi2 thin-films were grown on Si(100) and Si(111) substrates. The thin-films grown on Si(100) and Si(111) substrates were polycrystalline and monocrystalline structures, respectively. The values of band-gap energy calculated from transmittance measurements were 0.71-0.72 eV. From Raman scattering measurements, it was found that the distortion due to the lattice mismatch between a β-FeSi2 thin-film and a Si substrate originates in the β-FeSi2/n-Si interface. Moreover, the fine crystals of β-FeSi2 existed in an amorphous thin-film which was grown on Si(111) substrate at room temperature (RT).

From van der Pauw measurements, conduction type, carrier concentration and Hall mobility were p-type, 1018-1021 cm−3 and 200-500 cm2/Vsec, respectively. The p-n diode characteristics of these heterostructure diodes were investigated by I-V and C-V measurements. The results indicate that the carrier distribution agrees with an ideal one-sided slope junction.

We have studied the nucleation and growth of alumina by metalorganic chemical vapor deposition (MOCVD). The deposition of alumina films was carried out on Si(100) in a horizontal, hot-wall, low pressure chemical vapor deposition (CVD) reactor, using aluminum acetylacetonate{Al(acac)3}as the CVD precursor. We have investigated growth of alumina films as a function of different CVD parameters such as substrate temperature and total reactor pressure during film growth. Films were characterized by optical microscopy, X-ray diffractometry (XRD), scanning electron microscopy (SEM), cross-sectional SEM, and secondary ion mass spectrometry (SIMS) compositional depth profiling. The chemical analysis reveals that the carbon is present throughout the depth of the films.

Fractal pattern evolution of NiSi2 grains on a Si surface was induced by high current pulsed Ni ion implantation into Si wafer using metal vapor vacuum arc ion source. The fractal dimension of the patterns was found to correlate with the temperature rise of the Si substrate caused by the implanting Ni ion beam. With increasing of the substrate temperature, the fractal dimensions were determined to increase from less than 1.64, to beyond the percolation threshold of 1.88, and eventually up to 2.0, corresponding to a uniform layer with fine NiSi2 grains. The growth kinetics of the observed surface fractals was also discussed in terms of a special launching mechanism of the pulsed Ni ion beam into the Si substrate.

In the present work by means of measurements of RHEED intensity the research of the arrangement of tin atoms on vicinal surfaces of GaAs crystals was carried out. The orientation of crystals was close to (001). The intensity of diffracted electrons was measured in different points of the diffraction picture to reveal the arrangement of tin atoms on terraces or on edges of terraces. It was shown that tin atoms may decorate edges of terraces and thus form chains. Concentrations of tin atoms located on terraces and their edges were established. It was revealed, that tin atoms decorate edges of terraces only at rather high temperatures of a substrate.

Colossal magnetoresistive thin films have shown a large electric-pulse-induced resistivity change effect in zero magnetic field and at room temperature. The resistance of such films can be both decreased and increased through multiple nonvolatile intermediate levels by short electrical pulses. The effect provides a potential to develop a novel nonvolatile memory with high density, fast speed, and low power-consumption. An example of this effect has been seen for Pr0.7Ca0.3MnO3 films within which the thermal behavior of the film revealed a method for signal enhancement through annealing. An increase of 700% of the resistance ratio has been demonstrated for a film annealed at 170oC for 30 min. The effect is also observed to be active at room temperature but inefficient at low temperatures, which is interestingly contrary to the behavior of the colossal magnetoresistance effect and provides a clue to understanding the effect.

MgO thin films having different defect densities are explored in this study using metastable impact electron spectroscopy (MIES), ultraviolet photoelectron spectroscopy (UPS), temperature programmed desorption (TPD), and scanning tunneling microscopy (STM). Surface point defects on MgO exhibit themselves in both the MIES and UPS spectra as a feature approximately 2 eV above the valance band, whereas extended defects are only observed spectroscopically as a broadening of the O 2p band. The interaction of NO and N2O with the MgO surface as a function of surface defect density is explored. Upon adsorption on MgO thin films at 100K, both NO and N2O show the development of three features which coincide with a standard gas phase N2O spectrum. The saturation coverage of N2O from NO adsorption increases with increasing defect density, indicating that defect sites are mainly responsible for N2O formation. STM images confirm the increase of thin film defect density upon thermal quenching.

We introduce a method to build up organic/organic and organic/inorganic multilayer films composed of cationic poly(allylamine hydrochloride) (PAH) and negatively charged poly(sodium 4-styrenesulfonate) (PSS) or inorganic cadmium sulfide (CdS) nanoparticles using a spinning process. Since the deposition of each layer is made at a high spinning speed, the adsorption time for the formation of a homogeneous thin layer takes only 8 to 15 seconds. The adsorbed film thickness per bilayer can be easily controlled from about 5Å to 40Å by varying the spinning speed (Ω) and the mole concentration of polyelectrolytes. We also demonstrated with X-ray reflectivity that the alternating organic/inorganic ultrathin films fabricated by the spin SA process retain highly ordered internal structure in comparison with those prepared by the conventional SA process.

Abstract:Low temperature chemical vapor deposition of tungsten, tungsten carbide and tantalum carbide films on SiO2/Si(100) surfaces was studied by X-ray photoelectron spectroscopy (XPS) and electron microscopy. Tungsten carbide films were deposited using the W(CO)6 precursor with and without ethylene over temperatures ranging from 250 to 500 °C. The films grown without ethylene contained approximately 13 % carbon and 6 % oxygen. Cross section scanning electron microscopy imaging of the films grown at various temperatures without ethylene shows a polycrystalline microstructure, and the grain size increases dramatically as the growth temperature increases. Introducing ethylene increased carbon incorporation and changed the microstructure to amorphous-like. The tungsten to carbon ratio was approximately 2 at growth below 500 °C, and reached ~ 1.2 above 500 °C. The tantalum carbide films were deposited in a plasma enhanced chemical vapor deposition (PECVD) process using methane. The PECVD tantalum carbide films were conductive with a resistivity of ~1000 µΩ cm, which is about one order of magnitude lower than thermally grown films from pentakisdimethylamino tantalum.

We employ surface-embedded-atom-method potentials to investigate the diffusion barriers of vacancies diffusing over and near steps on the low index faces of silver. Barriers for vacancy terrace diffusion, diffusion over step-edges, and diffusion along step edges, including around corners, are calculated. Vacancies are significantly less mobile than adatoms and have large Ehrlich-Schwoebel (ES) barriers on all three faces. For Ag(100) the diffusion barrier for vacancies along step-edges is virtually the same (474 meV) as on the terrace. As in diffusion near the step edge, vacancies encounter a significant increase (213 meV) in the activation barrier when diffusing around the corner of a vacancy island (the corner analogue of the ES barrier), but the excess barrier around a kink all but disappears because exchange diffusion is favorable there. The consequences of the vacancy diffusion barriers on 3D pitting and on island diffusion and coarsening are discussed.

Epitaxial Al2O3 films have been successfully grown on an oxidized silicon substrate by the ionized beam deposition using an Al ion beam in oxygen environments. The crystalline quality dependence of the Al2O3 films on the growth temperatures was investigated. Using in situ reflection high energy electron diffraction, the orientation relationships between epitaxial Al2O3 films and Si substrate were found to be (100) Al2O3//(100) Si with [110] Al2O3//[110] Si and (111) Al2O3//(111) Si with [112] Al2O3//[112] Si. The stoichiometry of the films was found to be similar to that of sapphire from XPS measurements.

Nitride materials are of interest for a wide variety of applications, including wear-resistant coatings, insulating layers, high-temperature semiconductor devices, and short-wavelength emitters and detectors. TiN and AlN appear to be particularly amenable to crystalline thin film deposition, with stoichiometric material easily obtained even without the use of active nitrogen species. This paper describes the growth of crystalline AlN and TiN thin films on silicon and sapphire substrates using a KrF excimer laser (λ = 248 nm) to ablate elemental metallic targets, and an inductively-coupled RF plasma source to supply active nitrogen species. Growth was monitored in-situ using reflection high-energy electron diffraction (RHEED), and films were characterised using fourier-transform infrared spectroscopy (FTIR) and electron microscopy techniques. Optimised growth conditions led to single-crystal growth of TiN on both substrates, but only polycrystalline AlN was formed directly. Use of a TiN buffer layer on (0001) sapphire led to the successful growth of a single-crystal AlN layer as confirmed by RHEED and high-resolution transmission electron microscopy (HRTEM).