1. SURFACE TRANSFORMATIONS AND GROWTH OF NANOCRYSTALS ON Au-COVERED GaAs and InP CRYSTALS Prof. Dr. Imre MOJZES MINAEST-NET TU Berlin/FhG-IZM, Berlin, Germany 22 April 2005

2. Participants Imre Mojzes A, Sándor Kökényesi B, István A. Szabó C, Istvan Ivan B, Béla Pécz D A – Budapest University of Technology and Economics, Department of Electronics Technology H-1111 Budapest Goldmann Gy. ter 3. mojzes@ett.bme.hu B – Debrecen University, Department of Experimental Physics H-4026 Debrecen, Bem ter 18/a Hungary kiki@tigris.klte.hu C - Debrecen University, Department of Solid State Physics H-4010 Debrecen POB 2 Hungary aszabo@tigris.klte.hu D – Institute of Technical Physics and Material Sciences of the Hungarian Academy of Sciences pecz@mfa.kfki.hu

3. Abstract We present a simple method of nanocrystal growth during the heating of Au-covered GaAs single crystals in a closed quartz ampoule. 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 o 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 o C. These nanostructures were indentified by SEM and TEM measurements as -Ga 2 O 3 and a nonstoichiometric 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 -Ga 2 O 3 nanowires was dominated by the vapor-liquid-solid mechanism.

4. Roots Interaction of gold based contacts with compound semiconductors GaAs, InP, InAs, GaSb, InSb, GaP.. InGaAlAs, GaAsP GaAs microwave semiconductor devices

5. Experimental n – GaAs - 50nm Au HEATING quartz ampoule (10 -3 torr, H 2 O, saturated As 2 ) in SEM (high pumping rate) GaAs, InP

6. Steps Sample preparation (Debrecen+Budapest) Heat teratment (Debrecen) SEM, HVTEM (Budapest)

7. Results I. GaAs/Au nanowires and nanotubs InP/Au only nanowires

8. Results II. GaAs-Au

9. Results III. nanotubes

10. Partners we need Modelling Electrical measurements on the nanowires and nanotubes Application Fractalmathematical investigations

11. Contacts Prof. Dr. Imre MOJZES Budapest University of Technology and Economics Department of Electronics Technology H-1111 Budapest Goldmann Gy. T. 3. Bld. V2 255. mojzes@ett.bme.hu +36-1-463-2740 mojzes@ett.bme.hu