Gottfried Hochleitner

Atomic Scale Alignment of Copper-Germanide Contacts for Ge Nanowire Metal Oxide Field Effect Transistors

In this letter, we report on the formation, of copper-germanide/germanium nanowire (NW) heterostructures with atomically sharp interfaces. The copper-germanide (Cu3Ge) formation process is enabled by a chemical reaction between metallic Cu pads and vapor-liquid-solid (VLS) grown Ge-NWs. The atomic scale aligned formation of the Cu3Ge segments is controlled by in situ SEM monitoring at 310 degrees C thereby enabling length control of the intrinsic Ge-NW down to a few nanometers. The single crystal Cu3Ge/Ge/Cu3Ge heterostructures were used to fabricate p-type Ge-NW field effect transistors with Schottky Cu3Ge source/drain contacts. Temperature dependent I /V measurements revealed the metallic properties of the Cu3Ge contacts with a maximum current density of 5 x 10(7) A/cm2. According to the thermoionic emission theory, we determined an effective Schottky barrier height of 218 meV.

Electron beam induced deposition of iron nanostructures

Electron beam induced deposition is among the most prospective methods for size- and position-controllable nanofabrication of three-dimensional structures. Direct-write maskless nanostructure fabrication was performed with a scanning electron microscope. Three-dimensional iron structures were obtained by locally confined electron induced dissociation of an iron carbonyl (Fe(CO)5) precursor. Vertical nanopillars consisting of Fe with O and C contaminations were deposited. Two different growth regimes—electron induced growth and autonomous growth—were observed. The precursor pressure was shown to have a significant influence on the growth mode.

Focused electron beam induced deposition of gold catalyst templates for Si-nanowire synthesis

A new approach using focused electron beam induced deposition (FEBID) to deposit catalyst particles is reported for the synthesis of single crystalline silicon nanowires (SiNWs) grown by low pressure chemical vapor deposition (LPCVD). The FEBID deposited gold dot arrays fabricated from an acac-Au(III)-Me(2) precursor were investigated by AFM and EDX. The depositions were found to form a sharp tip and a surrounding halo and consist of only 10 at.% Au. However, SiNWs could be synthesized on the deposited catalyst using the vapor-liquid-solid (VLS) method with a mixture of 2% SiH(4) in He at 520 °C. NW diameters from 30 nm up to 150 nm were fabricated and the dependency of the NW diameter on the FEBID deposition time was observed. TEM analysis of the SiNWs revealed a [110] growth direction independent of the NW diameter. This new method provides a maskless and resistless approach for generating catalyst templates for SiNW synthesis on arbitrary surfaces.

Evaluation of chamber contamination in a scanning electron microscope

In any scanning electron microscope (SEM) organic contamination of the vacuum chamber leads to undesired material deposition resulting in artifacts in imaging or compromises focused electron beam induced processes like etching (FEBIE) [S. Matsui and K. Mori, Appl. Phys. Lett 51, 1498 (1987)] or deposition (FEBID) [S. Matsui and K. Mori, J. Vac. Sci. Technol. B 4, 299 (1986); W. F. van Dorp and C. W. Hagen, J. Appl. Phys. 4, 081301 (2008)]. This effect can also be used on purpose as a method to evaluate the contamination level of a SEM. With a standardized process for controlled deposition from residual gas, a method to evaluate the contamination level of an electron microscope quantitatively and reproductively was developed. Additionally, this method not only allows monitoring the contamination level of a SEM over its lifetime. Also the impact of various deposition parameters on the extent of contamination deposition has been investigated systematically. This method also allows comparing the status of dif...

Novel method for cleaning a vacuum chamber from hydrocarbon contamination

A novel method for cleaning a high vacuum chamber is presented. This method is based on concurrent in situ high-energetic UV light activation of contaminants located in the residual gas and at the vacuum chamber surfaces as well as the in situ generation of highly reactive ozone. Ozone oxidizes the contaminants to volatile species. Investigations by energy-dispersive x-ray analysis of residual gas depositions and mass-spectroscopy measurements of the residual gas in the vacuum chamber identify the contaminant species as hydrocarbons. After a cleaning period of 8 h, a decrease in measured chamber contamination by about 90% could be achieved according to atomic force microscope analysis. Mass spectroscopy measurements using a residual gas analyzer indicate the creation of volatile, carbonaceous species during the cleaning process.

Crystallinity-retaining removal of germanium by direct-write focused electron beam induced etching

In this work, a well-controllable, direct-write, resistless, and crystallinity-retaining etching process for germanium using a focused electron beam with nanometer resolution has been developed. This process allows for precise, local, and efficient removal of germanium from a surface without showing any spontaneous etching effects. This focused electron beam induced etching process of germanium substrates employs pure chlorine gas as etchant. The presented process was carried out in a conventional scanning electron microscope equipped with a custom-tailored gas injection system. The etch rate of this etching process was observed to be up to 0.32 μm3 min−1 or 12 nm min−1 for an area of 1.5×1.5 μm2. The influence of various etching parameters such as electron beam current, acceleration voltage and chlorine gas flow on the etch rate as well as the shape of the etch pits have been studied systematically by atomic force microscopy analysis. It is demonstrated that etching of amorphous germanium films can be pe...