Engineering of bulk and nanostructured GaAs with organic monomolecular films [Elektronische Ressource] / Klaus Adlkofer

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Technische Universität München Physik Department Lehrstuhl für Biophysik E22 Engineering of Bulk and Nanostructured GaAs with Organic Monomolecular Films Klaus Adlkofer Vollständiger Abdruck der von der Fakultät für Physik der Technischen Universität München zur Erlangung des akademischen Grades eines Doktors der Naturwissenschaften genehmigten Dissertation. Vorsitzender: Univ.-Prof. Dr. M. Kleber Prüfer der Dissertation: 1. Univ.-Prof. Dr. E. Sackmann 2. Hon.-Prof. Dr. P. Fromherz Die Dissertation wurde am 01.12.2003 bei der Technischen Universität München eingereicht und durch die Fakultät für Physik am 16.12.2003 angenommen. Danke Danke! Prof. Erich Sackmann für die Möglichkeit an seinem Lehrstuhl zu promovieren. Dr. Motomu Tanaka für seine hervorragende Betreuung und vieles mehr. Motomus Gruppe und den Insassen des neuen und alten Diplomandenzimmers Oliver Purrucker, Florian Rehfeldt, Murat Tutus, Joachim Hermann, Michael Nikolaides, und Stephan Rauschenbach für eine interessante und ereignisreiche Zeit. Ein paar Ex-E22ern, Dr. Heiko Hillebrandt, Dr. Matthias F. Schneider und Dr. Gerald Wiegand für die verschiedenste Unterstützung bei dieser Arbeit. Allen übrigen E22ern und Ehemaligen für die einzigartige Atmosphäre und Hilfe in jeder Situation. Prof. Gerhard Abstreiter (Walter Schottky Institut, TU München) für die Diskussionen und Zusammenarbeit im Bereich der Nanostrukturen. Dr.

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Publié le 01 janvier 2003
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Technische Universität München Physik Department
Lehrstuhl für Biophysik E22
Engineering of Bulk and Nanostructured GaAs with
Organic Monomolecular Films
Klaus Adlkofer
Vollständiger Abdruck der von der Fakultät für Physik der Technischen Universität München zur Erlangung des akademischen Grades eines Doktors der
Naturwissenschaften genehmigten Dissertation. Vorsitzender: Univ.-Prof. Dr. M. Kleber Prüfer der Dissertation:  1. Univ.-Prof. Dr. E. Sackmann  2. Hon.-Prof. Dr. P. Fromherz
Die Dissertation wurde am 01.12.2003 bei der Technischen Universität München eingereicht und durch die Fakultät für Physik am 16.12.2003 angenommen.
Danke
Danke!
Prof. Erich Sackmannfür die Möglichkeit an seinem Lehrstuhl zu promovieren. Dr. Motomu Tanakafür seine hervorragende Betreuung und vieles mehr. Motomus Gruppe und den Insassen des neuen und alten Diplomandenzimmers Oliver Purrucker,Florian Rehfeldt,Murat Tutus, Joachim Hermann,Michael Nikolaides, undStephan Rauschenbach für eine interessante und ereignisreiche Zeit. Ein paar Ex-E22ern,Dr. Heiko Hillebrandt,Dr. Matthias F. Schneider undDr. Gerald Wiegandfür die verschiedenste Unterstützung bei dieser Arbeit. Allen übrigenE22ern undEhemaligen die einzigartige Atmosphäre und Hilfe in für jeder Situation. Prof. Gerhard Abstreiter Schottky Institut, TU München) für die (Walter Diskussionen und Zusammenarbeit im Bereich der Nanostrukturen. Dr. Marc Tornow(Walter Schottky Institut, TU München),Sebastian LuberundUli Rantfür die gute und fruchtbare Zusammenarbeit im Bereich der 2DEGs. Prof. M. Grunze (Univ. Heidelberg) und seiner Gruppe für viele wichtige Elemente dieser Arbeit. Dr. Wolfgang Eckfür das Bereitstellen der 4-Mercaptobiphenyle. Dr. Michael ZharnikovundDr. Andrey Shaporenko für die große Hilfe bei den NEXAFS und HRXPS Messungen. Prof. Armin Gölzhäuser Bielefeld) und (Univ.Anne Paul für das e-beam crosslinken der 4-Substituierten-4-mercaptobiphenyle. Prof. Abraham Ulman Univ. Brooklyn, NY, USA) für fruchtbare (Polytchnic Diskussionen und die 4-Substituierten-4-mercaptobiphenyle.
MeinenElternfür die langjährige Unterstützung. Karin Bucher, die immer für mich da war.
Table of Contents
Table of Contents
1SUMMARY .........................................................................................1
2INTRODUCTION ................................................................................3
3MATERIALS, PREPARATION AND METHODS...............................7
3.1MATERIALS.............................................................7........................................3.2PREPARATION.................................9................................................................3.3MEASUREMENTMETHODS..11............................................................................3.3.1Atomic Force Microscopy ................................................................................................ 113.3.2Ellipsometry ..................................................................................................................... 133.3.3Spectroscopic Techniques .............................................................................................. 153.3.3.1X-Ray Fine Structure Spectroscopy ................................................................... 15Near Edge 3.3.3.2High Resolution X-Ray Photoelectron Spectroscopy............................................................ 163.3.4 ........................................................................................... 18Contact Angle Measurement3.3.5Electrochemical Measurements ...................................................................................... 193.3.5.1Cyclic Voltammetry ............................................................................................................... 203.3.5.2Impedance Spectroscopy ..................................................................................................... 214OPTIMIZATION OF GRAFTING CONDITIONS...............................254.1IMPACT OFSOLVENTS................2...5.................................................................4.2IMPACT OFTEMPERATURE............................................................................2..75STRUCTURAL ANALYSIS IN DRY STATES..................................285.1SURFACETOPOGRAPHY................................2.8................................................5.2FILMTHICKNESS03............................................................................................5.3MOLECULARORIENTATION ANDCHEMICALCOMPOSITION.........................31........5.3.1Molecular Orientation....................................................................................................... 315.3.2Chemical Composition..................................................................................................... 366STABILITY AND PROPERTIES IN ELECTROLYTE ......................40
6.16.26.3
WETTING ANDSURFACEFREEENERGY.........................................04..................ELECTROCHEMICALPROCESSES ACROSS THEINTERFACE........3...4.....................STABILITY ANDINTERFACEPROPERTIES......54....................................................
7
 Table of Contents
FUNCTIONALIZED GAAS-BASED 2DEG DEVICE ....................... 49
7.1SYSTEM ANDDEVICE..................................................................................... 497.1.1The Two-Dimensional Electron Gas System ................................................................... 497.1.2Device .............................................................................................................................. 507.2DIPOLEMOMENT OFGRAFTEDMOLECULES.................................................... 527.3STABILITY ANDSENSITIVITY AGAINSTPOLARSOLVENTS................................... 567.4STABILITY INAQUEOUSELECTROLYTE............................................................ 598CONCLUSIONS .............................................................................. 60
LITERATURE ........................................................................................ 62
PUBLICATIONS .................................................................................... 73
1 Summary
1 Summary
1
This thesis deals with a new method to engineer stoichiometric gallium arsenide (GaAs) [100] surfaces by deposition of organic monomolecular films, which can be used as stable and functional platforms for the design of novel bio-inspired semiconductor devices. Here, instead of commonly used inorganic insulators, a new class of self-assembled monolayers (SAMs) composed of 4-mercaptobiphenyl derivatives (X-MBPs) is used to stabilize the GaAs/electrolyte interface as well as to functionalize the GaAs surface. These functional organic domino-like molecules with rigid and bulky biphenyl backbones are chosen to accomplish high surface stabilities against the degradation in air and in water, and to provide various chemical functions to the surface via flexible 4-substitutions.
InChapter 4parameters, solvent polarity and temperature, which, two dominant determine the film qualities were systematically changed to optimize the grafting conditions of the X-MBPs. Qualities of the SAMs were evaluated in terms of the thickness using ellipsometry and the electrochemical stability checked by impedance spectroscopy. InChapter 5, the optimized SAMs and the bare GaAs (prepared by wet chemical etching) were characterized using various surface sensitive techniques in dry states, i.e. either in ambient or in vacuum. Atomic force microscopy (AFM) implied that the surfaces of SAMs have the comparable smoothness to bare GaAs, while ellipsometry measurements verified the monolayer formation. Near edge x-ray adsorption fine structure (NEXAFS) spectroscopy yielded the tilt angle of highly ordered MBP backbones to the surface normal. Furthermore, high resolution x-ray photoelectron spectroscopy (HRXPS) confirmed the covalent binding of sulfur and arsenide, and demonstrated the high chemical stability of the engineered surface against the oxidation in ambient.
InChapter 6, the functionalized GaAs surfaces were characterized in contact with water. Firstly, the surface free energies were calculated from the contact angles of different liquid droplets, which provide quantitative measures for the surface compatibilities to lipid membranes and biopolymers. In the next step, the
2
 1 Summary
electrochemical characterizations of the functionalized GaAs in physiological electrolytes were carried out by cyclic voltammetry and AC impedance spectroscopy. Cyclic voltammetry demonstrated that the grafting of SAMs resulted in a significant reduction of charge transfer across the GaAs/electrolyte interface. Furthermore,
impedance spectroscopy experiments denoted excellent electrochemical stabilities of the monolayer-coated GaAs in physiological electrolytes for more than 20 h. Chapter 7the direct application of the established engineering protocol onintroduces the planar FET with a Hall-bar configuration, where the two-dimensional electron gas (2DEG) is confined in the vicinity of the GaAs surface. Here, the molecular dipoles from 4-substituents and the solvent polarities were found to influence the sheet resistance of the 2DEG significantly, suggesting that the functionalized FETs are highly sensitive to the surface dipole moments.
The surface engineering method developed in the present study demonstrated a reliable device stability for the operations of various GaAs-based semiconductors with well defined surface characteristics, and suggests its large potentials to fabricate new biofunctional devices by deposition of biopolymers and model cell membranes.