Sputter-etched Surface Research Articles

Superhydrophobicity produced by vapor deposition of a hydrophobic layer onto fine protrusions formed by sputter-etching of steels

Argon ion sputter-etching was applied to W–Mo–Cr–V high speed steel, Cr–Mo–V die steel, and type 304 and 316 austenitic stainless steels. Vapor-deposition of the polyethylene (PE) or 1H, 1H, 2H, 2H, -Perfluorodecyltriethoxysilane (PFDS) was carried out on the sputter-etched surface. The hydrophobicity was evaluated by measuring the contact angle (CA) of a water droplet on the surface. The sputter-etching formed fine and dense pillar- or cone-shaped protrusions with a diameter of 100nm to 1μm on the tool steels and the type 316 steel but cone-shaped protrusions with a diameter of more than 1μm on the type 304 steel. The surfaces of all the steels just after the sputter-etching revealed CAs smaller than 4.5°, or superhydrophilicity. On the other hand, all the steels that were sputter-etched and vapor-deposited with PE or PFDS produced CAs of more than 150°, or superhydrophobicity, except that the CA of the type 304 steel with micron-sized protrusions was 146°. The adhesion of the PFDS layer to the protrusions is much stronger than the PE layer, i.e. it is difficult to remove the PFDS layer by heating at 473K and ultrasonic cleaning in acetone.

Role of Plasmons in Improved Photovoltaic Devices : Nano Clusters of Sn and SnOx in SnO2 Films

Recently, plasmonic concepts have been used to increase absorption length of incident light and seperation of excess carriers in photovoltaic devices. Doped SnO2 films are used as transparent conducting oxide (TCO) in photovoltaic devices. Sputter etched surfaces of SnO2 films have nano clusters of Sn and SnOx. Valence bulk plasmons (VBPs) of nano clusters have been studied using ultraviolet photoelectron spectroscopy (UPS) in in-situ conditions. Transmission and atomic force microscopy (AFM) are used in ex-situ conditions to study surface morphology and optical properties of sputtered SnO2 thin films.

Room-temperature Wafer Bonding

Bonding technologies play important roles in MEMS fabrication processes, especially for reliability and commercial competitiveness. One of those technologies is wafer direct bonding. Conventional wafer direct bonding utilizes hydrogen bonds between hydroxyl groups on wafer surfaces. It has an advantage of pressure-less bonding; however, high temperature annealing step, required to achieve practical bonding strength, limits its application to MEMS devices. In wafer direct bonding, surface state of the wafers largely influences the bonding. Therefore, several surface treatments have been adapted. Surface activated bonding (SAB) utilizes sputter etching of the bonding surface in vacuum. The sputter etched surface is expected to be in an active state and form strong bonds at lower temperatures. Various materials such as silicon, compound semiconductors and metals can be bonded at room temperature. On the other hand, in case of SAB between oxide wafers, low temperature annealing, typically at 200oC, is effective to achieve strong bonding. This means that a simple model of bond formation between clean surfaces is not enough to explain the bonding process of SAB.

Structural And Compositional Modifications of III–V Ternary and Quaternary Compounds Induced by Ion Bombardment

ABSTRACTThe effect of low energy (0.5 to 5 keV) Ar+ beams on the surface structure and composition of monocrystalline ternary In0.53Ga0.47As and quaternary In0.70Ga0.30As0.64P0.36 films epitaxially grown by MO-VPE on InP (100) substrate has been investigated. Quantitative Auger electron spectroscopy has been used with the elemental standard method taking into account the electron diffraction effects. For both semiconductors, the outermost surface layer has been found to be Ga and In enriched. In the subsurface region, the Ga enrichment is even larger, at the expense of As and In. In the quaternary film, P is depleted in the surface as well in the subsurface region. Angular Resolved Auger Electron Spectroscopy is applied to the structural study of the sputter-etched surface. The nature and spatial extension of the ion-induced surface damage have been investigated at different energies, and doses of the primary ion beam. Is has been found that the resistance to the amorphization is strongly enhanced in InGaAs with respect to GaAs.

Effects of annealing on resistivity and on Schottky barrier heights of sputter-deposited MoSi2 films

MoSi2 films were deposited by rf sputtering from MoSi2 grains. The stoichiometry of the film was verified by the backscattering method. The effect of heat treatment on the resistivity of the film was studied by annealing the film up to 1000 °C in nitrogen atmosphere. After a 1000 °C anneal, resistivity of 90 μΩ cm can be achieved reproducibly. Measurements of hole and electron barriers of junctions between sputter-deposited MoSi2 films and either p- or n-Si are reported. For an as-deposited contact, the hole and electron barriers on p- and n-Si were 0.75 and 0.38 eV, respectively, for chemically etched surfaces. For sputter-etched surfaces, the hole barrier increased further to 0.83 eV and the electron barrier reduced to 0.32 eV. By annealing the diodes in nitrogen at 400 °C for 30 min, the hole barrier was lowered to 0.56 eV and the electron barrier was increased to 0.58 eV for both chemically etched and sputter-etched surfaces.

Native oxides on etched Zn3P2 surfaces studied by x-ray photoelectron spectroscopy

The native oxides formed on air exposed, etched bulk polycrystalline Zn3P2 were investigated in the as-etched condition, using x-ray photoemission spectroscopy. The sputter-etched surfaces appeared to be composed primarily of ZnO with a small concentration of P2O3 or phosphate underneath. The bromine-methanol etched surfaces were less oxidized, and the native oxides appeared to become predominantly of phosphorus compound oxides. P2O5 was not observed in either case.

Optoelectronic and structural properties of sputter etched surfaces of InP

The effects of sputter etching on the optoelectronic and structural properties of 〈100〉 surfaces of InP were investigated by photoluminescence (PL) and Raman scattering in conjunction with capacitance-voltage determinations of the density of surface state Nss. The surfaces were etched in an Ar+ plasma for 5 min with plasma power densities D up to 0.1 W cm−2. The near band edge PL intensity shows a striking dependence on D. Below the threshold for macroscopic structural damage, the behavior of the PL and the Nss are independent of each other. A movement of the Fermi level at the surface is invoked in order to explain the PL response.

Visible and ultraviolet reflectivity of Hg1−xCdxTe

The reflectivity and wavelength-modulated reflectivity of Hg1−xCdxTe samples were measured in the 2.0–8.8 eV energy range to determine the dependence of the spectral features E1, E1+Δ1,A, and B on composition and on temperature. Spectral features of mechanically polished surfaces and sputter-etched surfaces were broadened, decreased in magnitude, and shifted to lower energies than those features of Br2-etched surfaces. At low temperatures, the spectral features of chemically etched surfaces narrow appreciably more than polished or sputter-etched surfaces, indicating that at room temperature there is a large thermal contribution to the width of the spectral features of chemically etched surfaces.

Schottky-barriers on p-type GaInAs

On p-type Ga <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.47</inf> In <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.53</inf> As LPE-grown layers, Schottky diodes were fabricated with different metals and surface preparations. On chemically etched surfaces, diodes with ideality factors near unity but rather low breakdown voltages with soft breakdown were achieved. The barrier heights were between 0.4 and 0.7 eV depending on the work function of the metal. On sputter-cleaned surfaces the diodes exhibited high breakdown voltages and barrier heights of about 0.7 eV independent of the metal. Annealing of the diodes at 320°C resulted in reduced series resistances and barrier heights in the case of sputteretched surfaces. The junction seems to consist of two different barriers; the lower one is determined by an As segregation at the interface, whereas the higher one is caused by traps which are induced by the sputter process.

Species-specific densities of states of Ga and As in the chemisorption of oxygen on GaAs(110)

Auger line-shape measurements have been made to extract the variation in the local charge distribution around Ga and As sites for chemisorption of oxygen on cleaved and sputter-etched GaAs(110). A significant variation with changing oxygen coverage is observed in the Ga spectrum, with a much more subtle change in the As spectrum. The kinetics of oxygen chemisorption on the sputter-etched surface is much more rapid than that on the cleaved surface. The line-shape changes induced by oxygen on the two surfaces are, however, similar. Conclusions on the nature of the bonding and on the mechanism for adsorption at both low and high coverages are drawn.

Ellipsometric Measurement of Damage Depth Profiles for Ion Beam Processed Si Surface Layer

The damage depth profiles in ion-implanted or rf sputter-etched Si surface layers have been measured by combining ellipsometric measurement with step removal. The ellipsometric measurements were compared with those of Auger Electron Spectroscopy for the ion-implanted surfaces, and with oxidation Sirtl etching check measurements (OS check) for the rf sputter-etched surfaces. It was found that a damage peak position exists inside the surface layer, e.g. at a depth of about 700 Å for 70 keV phosphorus ion implantation in Si. This position exists at the surface side rather than at the dopant peak position. The change in the refractive index is caused primarily by the change from single crystal to the amorphous (damage) state. It is also verified that the damage region measured ellipsometrically corresponds to the distribution of oxidation-induced stacking faults (OSF) for rf sputter-etched specimens.

Surface Finishing of a Cemented Tungsten Carbide Chip due to Ion Beam Sputter-Etching

In contrast to the ion sputter-etching of hard and brittle materials like silicon, glass and quartz, the ion sputter-etched surface of metals becomes to be somewhat more roughly in general, even though the initial surface is finished mirror like. However, for cemented tungsten carbide, the roughness of the ion sputter-etched surface seems to be maintained very fine as it was initially, under certain working condition. In this experiment, the effects of ion incident angle (θ: stationary 0°–90° and uniformly changing), ion energy (E=9.3 keV 1.5 keV) and ion species (Ar and Kr) on the etched surface roughness of tungsten carbide chip have been mainly investigated. Moreover, the surface topography of the sputter-etched surface has been examined with electron microscope. As the results, it has been confirmed that the sputter-etched surface of cemented tungsten carbide chip can hold its roughness as the prefinished mirror like, for the ion energies of 0.5 keV and 1.0 keV of Ar at the uniformly changing incident angle, and also for 1.0 keV of Kr at the stationary incident angle of 60° and at the uniformly changing incident angle. Therefore, the ion beam sputter-etching can be used for the fine adjustment of dimensions of block gauge made of tungsten carbide.

Schottky Contact Characterization of Sputter-Etched Surface of GaAs and Its Recovery by Annealing

Schottky Contact Characterization of Sputter-Etched Surface of GaAs and Its Recovery by Annealing

Surface enrichment of In in evaporated Au–In films

The surface composition of evaporated Au(98%)–In(2%) alloy films has been investigated by Auger electron spectroscopy. Sputter etching showed the surface concentration to be markedly different from the bulk concentration. The In concentration on a freshly sputter-etched surface increases with time and reaches an equilibrium value of [inverted lazy s] 15 at.%, at room temperature. This In-enriched surface is believed to have the thermodynamically stable composition.