Dresden 2003 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
CPP: Chemische Physik und Polymerphysik
CPP 3: Biomoleküle
CPP 3.8: Vortrag
Montag, 24. März 2003, 12:00–12:15, ZEU/118
Examination of preparation methods of GaAs wafers for biological voltage sensors — •John P. Sutter1, Justin D. Smith2, Trevor R. Finlayson2, Christian Kirchner3, Markus Seitz3, and Uwe Klemradt4 — 1HASYLAB am DESY, Notkestrasse 85, 22607 Hamburg, Germany — 2School of Physics and Materials Engineering, Monash University, Clayton, Victoria 3800, Australia — 3Sektion Physik and Center for Nanoscience (CeNS), LMU München, Geschw.-Scholl-Pl. 1, 80539 München, Germany — 4RWTH Aachen, II. Physikalisches Institut, 52056 Aachen, Germany
High-resolution voltage sensors based on GaAs have been proposed to measure the µV to mV signals produced by living cells, owing to their high electrical sensitivity. However, GaAs in an aqueous environment gives off toxic As and AsO33−. Therefore, a protective barrier must be placed between the GaAs and the cells. The barrier should also prevent oxide layer growth that would pin the Fermi layer and make the sensor useless. A 400 Å layer of polymerized (3-mercaptopropyl)trimethoxy-silane (MPT) on the wafer’s surface appears to prevent leakage of toxic byproducts and to promote cell adhesion. We have used the RWTH reflectometer at HASYLAB beamline E2 to examine GaAs wafers subjected to the following combinations of treatments: (a) etch or no etch, (b) MPT "seedingNo-dq monolayer or no monolayer (prior to polymer deposition). Reference samples with no MPT layer were also investigated. A reflectivity simulation program was used to obtain information on the oxide and polymer layer thicknesses and densitites. The data confirm the importance of MPT monolayers for the growth of a proper barrier.