Imre Mojzes

Heat treatment parameters effecting the fractal dimensions of AuGe metallization on GaAs

Correlation was detected between the thermal treatment parameters of the AuGe–GaAs system and surface fractal structure. Structural entropic calculations were used to confirm the results obtained by fractal calculations.

Investigation of morphology and fractal behaviour on compound semiconductor surface after electrochemical layer removal

Abstract The electrochemical method is a very versatile tool for characterization and processing of compound semiconductors. In this paper we investigate the surface morphology and pattern formation of GaAs and InP surfaces after electrochemical layer removal. Different aqueous HCl based electrolites were used for the layer removal. The investigation of the surface pattern formation was carried out using the box counting method. The pictures of surface patterns were digitised and analysed using high resolution bitmap. The fractal dimension depends on the semiconductor materials, electrolyte and condition of etching, too.

Surface Transformations and Growth of Nanocrystals on Au-covered GaAs Crystals

We present a simple method of nanocrystal growth during the heating of Au-covered GaAs single crystals in a closed quartz ampoule, previously evacuated to 10-1 Pa. The process is the final stage of surface transformations in such crystals which include the disruption of initially continuous, 50 nm thick Au layer and formation of Au-particle fractals in the relatively low 300-500 °C temperature range and a next step, when a variety of crystalline nanowires and even nanotubes grows on the crystal surface during the further short-period heating up to 550-650 °C. These nanostructures were identified by SEM and TEM measurements as b-Ga2O3 and a non-stoichiometric arsenic oxide. It is supposed that the growth of few nanometer thick arsenic oxide tubes follows the vapour-solid mechanism, whereas the catalytic Au-metal growth of thicker b-Ga2O3 nanowires was dominated by the vapour-liquid-solid mechanism.

Some remarks to the nanowires grown on Ill-V substrate

In the present work nanowires are investigated, which were prepared with the help of encapsulated metal induced growth method on GaAs and InP substrate. As our former investigations show, we can receive nanowires with substrate-like composition in the case of InP. In the case of GaAs substrate the situation is entirely different, while the growth technology in both cases was the same. The difference between the nanoproducts in the cases of different substrates originate in the reactivity of the components, which is explained in the following considerations. Furthermore we have observed that the diameter of the nanowires depends on the electron energy of the irradiation. If the electron beam was 5 kV and 20 kV, the diameter lasting increases and decreases, respectively. This effect can be explained by the change of the nanowires structure influenced by the electron beam.

Metal diffusion and surface pattern formation on GaAs and As/sub 2/S/sub 3/ semiconductors

The possible changes of composition, phase transformations at the surface were investigated in GaAs samples, covered with 50 nm thick Au layer and annealed at different temperatures. Diffusion processes at metal-semiconductor interface determine the surface pattern formation, which has fractal structure. Comparison was made with interdiffusion processes in Au-amorphous As/sub 2/S/sub 3/ and Bi-As/sub 2/S/sub 3/ structures, which were found as useful for micro and macroscopic surface relief formation, optical recording due to the additional photo-stimulated diffusion.

Surface pattern formation and the volatile component loss of heat treated metallisations of InP

Palladium based metal systems can be used to make ohmic contacts to A/sup III/B/sup V/ compound semiconductors. A covering layer of gold is advantageous from the point of view of bonding as well. Gold palladium layers were studied on InP substrates. Samples were annealed in the vacuum chamber of a scanning electron microscope (SEM) and the volatile component loss (phosphorus) was monitored by a quadrupole mass spectrometer. The changes of the surface morphology were studied using the SEM images. It means that the change of surface morphology and the volatile component loss were monitored simultaneously. In the case of Pd/A/sup III/B/sup V/ samples a single characteristic peak due to the interaction taking place between the metallization and the substrate was observed on the volatile component loss vs. temperature curve. In this temperature range characteristic pattern formation can be detected. This surface morphology shows fractal behaviour. It is supposed that the giant volatile component loss originating from the interaction between the metallization and the substrate can be described using percolation theory.

The speed of dissemination of information about the realization of the fourth passive electronic circuit element measured by Google hits

This paper aims to demonstrate briefly that major scientific achievements spread through the Internet according to an exponential expression until a saturation point.

Fractal properties of heat treated metal-compound semiconductor structures

The heat treatment of metallized Au(10 nm)/InP(100), Au(30 nm)/InP(100), Au(85 nm)/InP(100) structures were studied by in situ scanning electron microscopy combined with mass spectrometry. Correlation was found between the surface morphology and the volatile component loss caused by the material interactions taking place during the heat treatment. Earlier experiments proved that the surface morphology can be characterized by its fractal dimension. In this paper the dependence of the fractal dimension of the surface pattern on the heat treatment temperature and on the metal thickness is described.

ELECTRICAL AND STRUCTURAL CHARACTERISATION OF NI/GE/N-GAAS INTERFACE

Abstract The structural and electrical behaviour of Ni\Ge layers deposited onto n -type GaAs by electron beam evaporation were studied. The samples have been annealed for 20 min at different temperatures in flowing forming gas—H 2 : N 2 (5% : 95%)—in a tube furnace. When the annealing temperature was increased the Schottky barrier heights calculated from I- V and C- V characteristics decreased, and the I- V characteristics of the samples heat treated at 600°C became linear. The contact resistance of the samples with linear characteristic was measured with Cox method. The calculated specific resistivity was 4.4×10 −4 ohmcm 2 in the case of sample heat treated at 550°C and 5.1×10 −5 ohmcm 2 after annealing at 600°C. In the sample annealed at 550°C protrusions appeared with the size of 20–30 nm at the interface of semiconductor-metal. Detectable amount of Ge was found in addition to Ni, As, and G in the protrusions. Moreover, those features contain significantly less Ga than As. The protrusions containing Ge play a role in the formation of the low barrier contact.

Empirical study on the impact of electronics on stock exchange indices

This paper explains the results of research into the impact of the electronics industry on the macroeconomic environment. The paper concludes that the following hypothesis can be verified: that information concerning the volumes of different electronic product categories contributes to explaining stock exchange indices.