Microstructural and surface characterization of thin gold films on n-Ge (original) (raw)
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Microstructural and surface characterization of thin gold films on n-Ge (1 1 1
Physica B-condensed Matter, 2009
Thin gold films were fabricated by vacuum resistive deposition on the n-Ge (111) wafers. The films were annealed between 300 and 600 1C. These resulting thin films were then characterised using scanning electron microscopy (field emission and back-scattering modes), Rutherford back scattering spectroscopy and time of flight secondary ion mass spectroscopy (TOF-SIMS). For temperatures below the eutectic temperature the distribution of both the gold and the germanium on the surface are uniform. Above the eutectic temperature, the formation of gold rich islands on the surface of the Germanium were observed. These changes in the microstructure were found to correspond to changes in the electrical characteristics of the diodes.
RBS investigation of annealed thin gold layers on crystalline Ge
In this work we report firstly on the behaviour of Schottky barrier diodes (SBD's) when subjected to thermal treatment after metallization. To better understand this, a systematic study of the interaction between thin gold films and crystalline germanium substrates was undertaken. Gold metal films having thicknesses of 30 and 100 nm have been prepared by means of thermal evaporation on bulk-grown (111) n-type germanium doped with Sb to a level of 2.5×10 15 cm -3 . Before metallization the samples were first degreased and then etched in a mixture of H 2 O 2 :H 2 O (1:5) for one minute. Subsequently the samples have been thermally treated in Ar-atmosphere for 10 minutes and at temperatures ranging from 300 to 600°C. Rutherford backscattering spectrometry (RBS) has been performed to estimate the composition of the as-deposited and thermally treated films. It was found, that the composition of the asdeposited film remains unchanged under thermal treatment up to 340°C. Between 340°C and 360°C a gold-rich layer containing a very small amount of germanium is formed. At 361°C this layer suddenly converts to a germanium-rich layer with a small amount of gold. This transition is accompanied by the formation of agglomerates on the surface of the substrate.
RBS investigation of annealed thin gold layers on crystalline germanium
Journal of Physics: Conference Series, 2008
In this work we report firstly on the behaviour of Schottky barrier diodes (SBD's) when subjected to thermal treatment after metallization. To better understand this, a systematic study of the interaction between thin gold films and crystalline germanium substrates was undertaken. Gold metal films having thicknesses of 30 and 100 nm have been prepared by means of thermal evaporation on bulk-grown (111) n-type germanium doped with Sb to a level of 2.5×10 15 cm -3 . Before metallization the samples were first degreased and then etched in a mixture of H 2 O 2 :H 2 O (1:5) for one minute. Subsequently the samples have been thermally treated in Ar-atmosphere for 10 minutes and at temperatures ranging from 300 to 600°C. Rutherford backscattering spectrometry (RBS) has been performed to estimate the composition of the as-deposited and thermally treated films. It was found, that the composition of the asdeposited film remains unchanged under thermal treatment up to 340°C. Between 340°C and 360°C a gold-rich layer containing a very small amount of germanium is formed. At 361°C this layer suddenly converts to a germanium-rich layer with a small amount of gold. This transition is accompanied by the formation of agglomerates on the surface of the substrate.
Gold assisted molecular beam epitaxy of Ge nanostructures on Ge (100) Surface
2012
We report on the gold assisted epitaxial growth of Ge nanostructures under ultra high vacuum (UHV) conditions (≈3× 10 -10 mbar) on clean Ge (100) surfaces. For this study, ≈2.0 nm thick Au samples were grown on the substrate surface by molecular beam epitaxy (MBE). Thermal annealing was carried out inside the UHV chamber at temperature ≈ 500°C and following this, well ordered gold nanostructures placed on pedestal Ge were formed. A ≈ 2 nm Ge film was further deposited on the above surface while the substrate was kept at a temperature of ≈500°C. The height of the Ge (pedestal) underneath gold increased along with the formation of small Ge islands. The effect of substrate temperature and role of gold on the formation of above structures has been discussed in detail. Electron microscopy (TEM, SEM) studies were carried out to determine the structure of Au -Ge nano systems.
Gold-Germanium Contacts on Gallium Arsenide
Le Journal de Physique Colloques
The gold-germanium/gallium arsenide interface was investigated using atom-probe analysis and transmission electron microscopy. When thin films were deposited on an oxidized surface small islands formed. No gold or germanium was detected between islands. One island was analysed and it contained germanium, gold and a substantial amount of oxygen. No outdiffusion of gallium or arsenic to the island was observed.
Advances in Atom and Single Molecule Machines, 2012
The demand to discover new, alternative solutions in future electronics has currently focused the attention on the possible use of single atomic wires and conductive mesa pads as components in electronic circuits. For such applications, we need a good knowledge of structural and electronic properties of 1D and 2D conductive nanostructures fabricated on large and/or moderate band gap semiconductor surfaces. This chapter is reporting on case studies invoking preparation of well organized atomic wires and 2D conductive pads by self-assembly of gold atoms on clean, reconstructed Ge(001) surface. Structural characterization of the fabricated nanostructures was performed with atomic resolution on low temperature scanning tunneling microscope (LT-STM) and multi-probe STM designed by Omicron Nanotechnology GmbH. Using the far field, high resolution scanning electron microscope (SEM), the pre-prepared nanostructures were identified after an UHV transfer into a multi-probe station of the system, and their surface conductance was measured with two STM probes. The conductance dependence as a function of the inter-probe distance confirmed 2D (surface) character of the Au rich nanostructures assembled on Ge(001).
Electrical characterization of defects introduced during metallization processes in n-type germanium
We have studied the defects introduced in n-type Ge during electron beam deposition (EBD) and sputter deposition (SD) by deep-level transient spectroscopy (DLTS) and evaluated their influence on the rectification quality of Schottky contacts by current-voltage (I-V) measurements. I-V measurements demonstrated that the quality of sputter-deposited diodes are poorer than those of diodes formed by EBD. The highest quality Schottky diodes were formed by resistive evaporation that introduced no defects in Ge. In the case of EBD of metals the main defect introduced during metallization was the V-Sb complex, also introduced during by electron irradiation. The concentrations of the EBD-induced defects depend on the metal used: metals that required a higher electron beam intensity to evaporate, e.g. Ru, resulted in larger defect concentrations than metals requiring lower electron beam intensity, e.g. Au. All the EBD-induced defects can be removed by annealing at temperatures above 325 1C. Sputter deposition introduces several electrically active defects near the surface of Ge. All these defects have also been observed after high-energy electron irradiation. However, the V-Sb centre introduced by EBD was not observed after sputter deposition. Annealing at 250 1C in Ar removed all the defects introduced during sputter deposition.
Properties of electrodeposited germanium thin films
Physica status solidi, 2014
In this paper, the results of Ge film deposited by electroplating method was studied and showed the possibility of making a NIRS sensor by the Ge film. Cu/Ti double layer structure could use the cathode electrode on the glass substrate during the GeCl 4 electroplating. The deposition rate of electroplating Ge film was 100 nm/h, however, that rate was improved to 570 nm/h by introducing a spacer between Cu thin film and extraction electrode and Ar gas bubbling. The oxygen content of as-deposited film was about 10%, however, this value reduced to lower than 1% by using the Ar bubbling. The deposited film was amorphous and its optical band gap was 0.73 eV. 200 nm-thick Ge film was formed on flexible substrate by electroplating method.
Structure and Morphology of Annealed Gold Films Galvanically Displaced on the Si(111) Surface
Journal of Physical Chemistry C, 2007
ABSTRACT The effects of thermal treatment in ultrahigh vacuum (UHV) of gold films galvanically displaced on the Si(111) surface are studied with low-energy electron diffraction, Auger electron spectroscopy, atomic force microscopy, Kelvin probe force microscopy, and X-ray photoelectron spectroscopy. Annealing the galvanically displaced gold on Si substrates to 1100 K produces films with similar structure, composition, and morphology to annealed gold films evaporated on Si in UHV. The surface morphology is consistent with the Stranski−Krastanov growth mode. Compared to the unannealed film, an interfacial gold silicide layer forms upon annealing, although with limited improvement in adhesion. We report the formation of submicrometer Au/Si islands with narrow size dispersion, separated by deep trenches and with local order and shape dictated by the symmetry of the substrate. A mechanism for the formation of these islands is proposed.
Optical study of germanium nanostructures grown on a Si(118) vicinal substrate
Microelectronics Journal, 1999
Photoluminescence (PL) measurements were carried out on Si/Ge(n)/Si 0.7 Ge 0.3 /Si structures (n is varying from 1 to 7 ML) deposed by gas source molecular beam epitaxy (GS-MBE) on Si(100) surfaces and high index Si(118) vicinal surfaces. Ge nanostructures were confined on the top of the undulation of the Si 0.3 Ge 0.7 wetting layer, according to the Stranski-Krastanov growth mode. PL measurements reveal a correlation between the substrate orientation and the island morphology: square dots for (001) and wires for (118) surface orientation. The results suggest that the SiGe wetting layer is required to ensure a good dot size uniformity. The dependence of the luminescence on the excitation power and the PL decay time indicate that the luminescence transitions likely occur in a type-II band line up. Finally, the dotrelated PL persists up to room temperature which is very promising for optoelectronic device applications. ᭧