InformaApp - Publikationen

The conductive atomic force microscope (CAFM) has become an essential tool for the nanoscale electronic characterization of many materials and devices. When studying photoactive samples, the laser used by the CAFM to detect the deflection of the cantilever can generate photocurrents that perturb the current signals collected, leading to unreliable characterization. In metal-coated semiconductor samples, this problem is further aggravated, and large currents above the nanometer range can be observed even without the application of any bias. Here we present the first characterization of the photocurrents introduced by the laser of the CAFM, and we quantify the amount of light arriving to the surface of the sample. The mechanisms for current collection when placing the CAFM tip on metal-coated photoactive samples are also analyzed in-depth. Finally, we successfully avoided the laser-induced perturbations using a two pass technique: the first scan collects the topography (laser ON) and the second collects the current (laser OFF). We also demonstrate that CAFMs without a laser (using a tuning fork for detecting the deflection of the tip) do not have this problem.

Nachhaltig Elektrotechnik und Medientechnik

Zeitschriftenartikel

R.Y.Q. Fu, Alexander Hofer, Manuel Bogner, Günther Benstetter, H. Gruber

Differential 3ω method for measuring thermal conductivity of AIN and SI3N4 thin films

Thin Solid Films, vol. 591 Part B, pp. 267-270

2015

DOI: 10.1016/j.tsf.2015.03.031

Abstract anzeigen

The thermal conductivity λ of plasma enhanced chemical vapor deposited Si3N4 and sputtered AlN thin films deposited on silicon substrates were obtained utilizing the differential 3ω method. A thin electrically conductive strip was deposited onto the investigated thin film of interest, and used as both a heater and a temperature sensor. To study the thickness dependent thermal conductivity of AlN and Si3N4 films their thickness was varied from 300 to 1000 nm. Measurements were performed at room temperature at a chamber pressure of 3.1 Pa. The measured thermal conductivity values of AlN and Si3N4 thin films were between 5.4 and 17.6 Wm− 1 K− 1 and 0.8 up to 1.7 Wm− 1 K− 1, respectively. The data were significantly smaller than that of the bulk materials found in literature (i.e., λAlN = 250–285 Wm− 1 K− 1, λSi3N4 = 30 Wm− 1 K− 1), due to the scaling effects, and also strongly dependent on film thickness, but were comparable with literature for the corresponding thin films.

Nachhaltig Elektrotechnik und Medientechnik

Zeitschriftenartikel

Alexander Hofer, M. Mattheis, L. Hamann, M. Haas, Günther Benstetter, R. Zapf-Gottwick

Use of Coated-Metal Particles in Rear Busbar Pastes to Reduce Silver Consumption

IEEE Journal of Photovoltaics, vol. 5, no. 2, pp. 534-537

2015

DOI: 10.1109/JPHOTOV.2014.2388080

Abstract anzeigen

Reducing the amount of silver is one of the most important ways to reduce the cost of photovoltaic cells. The common way to reduce silver consumption on a cell is the reduction of the metal content in the paste. We present a new paste with silver-coated nickel particles, reducing the silver amount and still keeping the properties of silver related to oxidation and sintering. This paper shows the limits in conductivity due to porosity and oxidation of coated-metal particle pastes in comparison with silver pastes. Simulations and cell tests show that coated-metal particle pastes reduce silver consumption without decreasing the cell efficiency replacing busbar pastes. Coated-metal particle pastes are able to decrease silver consumption for rear-side busbars to c Ag <; 1.4 mg/cm 2 , leading to a conductivity σ BB = 1.110 5 S/cm, without decreasing cell or module efficiency. The conductivity of coated-metal particle pastes is too low using pastes with coated-metal particles as a replacement for the metallization paste for grid fingers but good enough to replace the silver paste for busbars with a cheap alternative.

Elektrotechnik und Medientechnik

Zeitschriftenartikel

Alexander Hofer, Günther Benstetter, R. Biberger, B. Wilke, H. Göbel

Scanning probe microscopy based electrical characterization of thin dielectric and organic semiconductor films

Microelectronics Reliability, vol. 53, no. 9-11, pp. 1430-1433

2013

Abstract anzeigen

Scanning probe microscopy (SPM) techniques offer various characterization methods for thin organic films. However, the majority of the electrical SPM measurements is currently performed in contact mode operation and may lead to severe damage at the surface of soft organic materials. This work shows the electrical characterization of organic insulator and semiconductor films by use of two SPM techniques operating with reduced lateral forces between SPM tip and sample. The first one is intermittent-contact scanning-capacitance-microscopy (IC-SCM) which is used for the detection of the local surface capacitance. The second one is torsional resonance tunneling-atomic-force-microscopy (TR-TUNA) which shows the local conductivity respectively relative film thickness of the sample. It is found that the tunneling current distribution across 50 nm thick organic insulating films is very homogeneous and that inhomogeneities in P3HT and Pentacene films can be pinpointed even if no topographical variations are observable.

Elektrotechnik und Medientechnik

Zeitschriftenartikel

Alexander Hofer, C. Leirer, Günther Benstetter, R. Biberger, G. Brüderl

Analysis of crystal defects on GaN based semiconductors with advanced scanning probe microscope technique

Thin Solid Films, vol. 544, no. Oktober, pp. 139-143

2013

Abstract anzeigen

The correlation of surface pits with leakage currents in gallium nitride (GaN) films are studied with scanning probe microscopy (SPM) techniques. The analyses were performed at both single n-GaN films grown on free-standing GaN and completely processed GaN light-emitting diode (LED) structures on sapphire substrates both grown by metal organic chemical vapor phase epitaxy. Topographical SPM images acquired with ultra-sharp probes were superimposed with current maps obtained by conductive atomic force microscopy (CAFM). The applicability of two different modifications of CAFM techniques has been studied. For both sample types, CAFM has revealed a clear correlation between forward-bias leakage current and locations of surface pits. In case of the LED structure, additional local current–voltage characteristics show that enhanced current conduction occurs in both forward and reverse bias on surface pit positions.

Elektrotechnik und Medientechnik

Vortrag

M. Brandt, Alexander Hofer, A. Greppmair, Tobias Berthold, Günther Benstetter

Nanoscale electrical conductivity of laser-sintered Ge nanoparticle layers

The 8th International Conference On Technological Advances Of Thin Films and Surface Coatings (ThinFilms 2016), Singapur, Singapur

Elektrotechnik und Medientechnik

Vortrag

M. Brandt, Alexander Hofer, A. Greppmair, Tobias Berthold, Günther Benstetter

Nanoscale characterization of laser-sintered Ge nanoparticle layers

2nd International Conference on Functional Integrated nano Systems (nanoFIS), Graz, Österreich

Nachhaltig Elektrotechnik und Medientechnik

Vortrag

Alexander Hofer, K. Schiebl, Günther Benstetter

Atomic Force Microscopy analysis of laser-sintered Germanium nanoparticles for thermoelectric applications

3rd International Congress on Energy Efficiency and Energy Related Materials (ENEFM), Oludeniz, Türkei

Nachhaltig Elektrotechnik und Medientechnik

Vortrag

M. Brandt, Alexander Hofer, A. Greppmair, Günther Benstetter

A review of physical characterization methods for nanostructured thermoelectric materials

Invited Talk

3rd International Congress on Energy Efficiency and Energy Related Materials (ENEFM), Oludeniz, Türkei

Elektrotechnik und Medientechnik

Vortrag

Alexander Hofer, C. Leirer, Günther Benstetter, R. Biberger, G. Brüderl

Analysis of crystal defects on GaN-based semiconductors with advanced scanning probe microscope techniques

Invited Talk

6th International Conference on Technological Advances of Thin Films & Surface Coatings (THINFILMS2012), Singapur, Singapur

Elektrotechnik und Medientechnik

Vortrag

Alexander Hofer, Günther Benstetter, R. Biberger, B. Wilke, H. Göbel

Scanning probe microscopy based electrical characterization of thin dielectric and organic semiconductor films

24th European Symposium on Reliability of Electron Devices, Failure Physics and Analysis (ESREF), Arcachon, Frankreich

Elektrotechnik und Medientechnik

Vortrag

Alexander Hofer, Manuel Bogner, Günther Benstetter, H. Gruber

The differential 3ω method for measuring the thermal conductivity of AIN and SI3N4 thin films

16th International Conference on Thin Films (ICTF16), Dubrovnik, Kroatien

Elektrotechnik und Medientechnik

Vortrag

Alexander Hofer, Tobias Berthold, Günther Benstetter

Selected Atomic Force Microscopy Methods for the Electrical Characterization of Thin Films and Devices

Invited Talk

4th International Advances in Applied Physics and Materials Science Congress & Exhibition (APMAS), Fethiye, Türkei

Elektrotechnik und Medientechnik

Vortrag

Alexander Hofer, Günther Benstetter, R. Biberger, B. Wilke, H. Göbel

Capacitance and Conductivity Mapping of Organic Films and Devices with Non-Contact SPM Methods

International Workshop on Scanning Probe Microscopy for Energy Applications, Mainz

Elektrotechnik und Medientechnik

Vortrag

Alexander Hofer, Günther Benstetter, R. Biberger, H. Göbel

Intermittent-Contact Scanning Capacitance Analysis of Thin Dielectric Films and Semiconductor Devices

Invited Talk

5th International Conference on Technological Advances of Thin Films & Surface Coatings, Harbin, China

Elektrotechnik und Medientechnik Maschinenbau und Mechatronik

Vortrag

Edgar Lodermeier, Alexander Hofer, B. Knoll, Günther Benstetter, Peter Breitschopf, Werner Frammelsberger

Intermittent Contact Scanning Capacitance Microscopy-First Results

Workshop on Scanning Probe Microscopy and Related Techniques, Villach, Österreich

Elektrotechnik und Medientechnik Maschinenbau und Mechatronik

Vortrag

Edgar Lodermeier, Alexander Hofer, D. Liu, Heiko Ranzinger, Günther Benstetter, Peter Breitschopf, W. Bergbauer, Werner Frammelsberger

Raster-Sonden-Mikroskopie (SPM) in der Fehler- und Zuverlässigkeitsanalytik

VDE Fehlermechanismen bei kleinen Geometrien, Grainau

Publikationen

Fakultät

Standort

Institut

Suche nach „[Alexander] [Hofer]“ hat 18 Publikationen gefunden

Über