Adsorption and desorption processes on beta-Ga2O3 and In2O3 surfaces studied via structural and thermo-/electrical investigations

透明半导体氧化物β-Ga 2 O3和In 2 O3代表了一类宽带隙半导体，在当今的研究和技术中引起了广泛的关注。虽然在过去的几十年中仅以多晶或非晶膜的形式使用，但最近的结果表明，具有受控电性能的块状单晶和结晶外延膜具有用作半导体的巨大潜力，其应用于透明微电子学、光电子学、短波长光子学和传感器器件中。在本研究项目中，我们将研究β-Ga 2 O3和In 2 O3大块单晶的明确表面的结构特性。重建有关的表面化学计量的变化和修改引起的吸附不同的分子气体，以及由覆盖与薄膜的镓和铟的β-Ga 2 O3和In 2 O3表面，分别，将得到解决。特别是，我们将研究不同的分子物种，如CO2，CH 4，H2，H2O，CH 3OH和C2 H6 O上的β-Ga 2 O3和In 2 O3，这是不太了解的吸附行为。结构和吸附性质的研究将通过快速原子衍射（FAD）技术和标准表面分析（如LEED和AES）的组合进行，以实验分析原子表面结构，即清洁和吸附物覆盖表面的弛豫，重建，终止，缺陷，台阶和形态。这些结构的调查是相关的，以改善生长过程中，如MOCVD外延异质结构和分子电子学领域的发展明确的表面结构。在传感器应用和非均相表面工程的框架内，吸附和解吸行为的详细知识是必不可少的。为了确定吸附和脱附过程中表面电位的变化，我们将测量电导率和噪声。特别是，在薄的单晶片和外延膜，我们将研究的热/电性能和它们的依赖于不同的分子物种的吸附和解吸行为。这些运输调查的动机是由明确定义的高品质的表面β-Ga 2 O3和In 2 O3的外延异质结构，新型电子器件，以及作为电导气体传感器的吸附层的表面的作用的基本理解的机会。

The transparent semiconducting oxides beta-Ga2O3 and In2O3 represent a class of wide band-gap semiconductors which attract much attention in research and technology today. While used in the last decades in the form of polycrystalline or amorphous films only, recent results show that bulk single crystals and crystalline epitaxial films with controlled electrical properties have great potential for use as semiconductors with applications in transparent micro-electronics, opto-electronics, short wavelength photonics and in sensor devices. Within this research project we will investigate the structural properties of well-defined surfaces of beta-Ga2O3 and In2O3 bulk single crystals. Reconstructions related to the variation of surface stoichiometry and modifications induced by the adsorption of different molecular gases as well as by the coverage with thin films of gallium and indium on beta-Ga2O3 and In2O3 surfaces, respectively, will be addressed. In particular, we will study the adsorption behaviours of different molecular species such as CO2, CH4, H2, H2O, CH3OH and C2H6O on beta-Ga2O3 and In2O3, which are less well understood. The investigations of the structural and adsorption properties will be performed by the combination of fast atom diffraction (FAD) technique and standard surface analytics like LEED and AES to analyze experimentally the atomic surface structure, i.e. the relaxation, reconstruction, termination, defects, steps and the morphology of the clean and adsorbate-covered surfaces. These structural investigations are relevant to improve growth processes such as MOCVD for epitaxial heterostructures and to the development in the field of molecular electronics on well-defined surface structures. In the framework of surface engineering for sensor applications and the heterogeneous photocatalysis the detailed knowledge of the adsorption and desorption behaviors is essentially. In order to determine the change of surface potential during adsorption and desorption processes, we will measure the electrical conductivity and noise. In particular, on thin single crystalline flakes and epitaxial films we will study the thermo-/electrical properties and their dependence on adsorption and desorption behaviors of different molecular species. These transport investigations are motivated by the opportunities which are given by the well-defined high-quality surfaces of beta-Ga2O3 and In2O3 for epitaxial heterostructures, novel electronic devices as well as a fundamental understanding of the role of surfaces as adsorption layers for conductometric gas sensors.