Section Thin Oxide Films

Section Thin Oxide Films

Mission

Epitaxial oxide layers act as an electrically active part of a device and offer new application prospects compared to bulk crystals and ceramics. By adding dopants or lattice strains, their functional properties can be specifically adapted to desired requirements. Smaller device structures in thin layers not only allow less material consumption, but also allow improved device parameters such as higher processor speeds or higher frequencies for filters or sensors. Our mission is to develop single crystal oxide films with optimized properties tailored to the application.

Research activities

The main focus of our work is on the deposition of oxide thin films with tailored semiconducting, dielectric or ferro/piezoelectric properties. The deposition methods for this purpose available at the IKZ are metal-organic vapor phase epitaxy (MOVPE) and pulsed laser deposition (PLD). Our activities include oxide films with thicknesses between a few nanometers and several micrometers with a large application potential in the field of high-power electronics, ferroelectric memory devices, piezoelectric sensors and energy harvesters.

Topics

Junior Research Group "Epitaxy of semiconducting Gallium Oxide"

Modern society relies on a wide range of electrical and electronic systems. To achieve this, the conversion of electrical energy must be carried out as efficient as possible. The material system β-Ga2O3 has due to its high bandgap of approx. 4.8 eV and the resulting theoretically high breakdown field strength the best prerequisites to become the high-performance material for next generation power applications. Therefore our mission is to achieve the predicted material properties through process development to pave β-Ga2O3 the way into power electronics.

The β-Ga2O3 MOVPE process development is focused on the investigation of the effects of the growth parameters and the type of doping on the electrical properties of the layers. Another focus is the homoepitaxial growth on differently oriented substrates and the influence on the generation of crystal defects. In addition, there are studies on increasing the growth rate by maintaining the good layer quality. In future, also alloys of the material with aluminium are planned to improve the positive properties of β-Ga2O3 even further.

Saud Bin Anooz, Raimund Grüneberg, Ta-Shun Chou, Andreas Fiedler, Klaus Irmscher, Charlotte Wouters, Robert Schewski, Martin Albrecht, Zbigniew Galazka, Wolfram Miller, Jutta Schwarzkopf, Andreas Popp
Impact of chamber pressure and Si-doping on the surface morphology and electrical properties of homoepitaxial (100) β-Ga2O3 thin films grown by MOVPE
J. Phys. D: Appl. Phys
DOI: 10.1088/1361-6463/abb6aa

Saud Bin Anooz, Raimund Grüneberg, Charlotte Wouters, Robert Schewski, Martin Albrecht, Andreas Fiedler, Klaus Irmscher, Zbigniew Galazka, Wolfram Miller, Günter Wagner, Jutta Schwarzkopf, Andreas Popp
Step flow growth of β-Ga2O3 thin films on vicinal (100) β-Ga2O3 substrates grown by MOVPE
Appl. Phys. Lett. 116, 182106 (2020)
DOI: 10.1063/5.0005403

Saud Bin Anooz, Andreas Popp, Raimund Grüneberg, Charlotte Wouters, Robert Schewski, Martin Schmidbauer, Martin Albrecht, Andreas Fiedler, Manfred Ramsteiner, Detlef Klimm, Klaus Irmscher, Zbigniew Galazka, Günter Wagner
Indium incorporation in homoepitaxial β-Ga2O3 thin films grown by metal organic vapor phase epitaxy
J. Appl. Phys. 125, 195702 (2019)
DOI: 10.1063/1.5090213

Contact

Dr. Andreas Popp

Ph. +49 30 6392 2844

Email

Resistive switching in SrTiO₃ thin films

For the use of SrTiO3 thin films for electronic applications, a basic understanding of the growth process and the resulting defects, especially oxygen vacancies, and interface phenomena is essential. Despite many years of experimental and theoretical efforts, this understanding is still limited. Our mission is therefore to fundamentally investigate and control the epitaxial layer growth of SrTiO3 and resistive switching as a function of growth parameters and the choice of substrate.

The deposition of SrTiO3 layers by metal-organic vapor phase epitaxy (MOVPE) allows a higher material perfection with respect to lower defect densities, smoother surfaces/interfaces and lower vacancy densities compared to pulsed laser deposition (PLD). In collaboration with the section "Experimental Characterization" the electrical and structural properties of epitaxial SrTiO3 layers are systematically investigated as a function of growth parameters as well as the influence of n-type doping.

Contact

Aykut Baki

Ph. +49 30 6392 3043

Email

Semiconducting BaSnO₃ thin films

Ferroelectric field effect transistors (FeFET) based on complex oxides have advantages over conventional transistors due to their low power consumption, higher switching velocity, higher memory densities and non-volatility. For such an application, especially barium stannate (BaSnO3) with its high charge carrier mobility, is a suitable oxide material. Our mission is the optimization of growth conditions of BaSnO3 and LaInO3 layers with respect to high carrier densities and mobility for the realization of a FeFET.

One of our activities within the project "BaStet" focuses on the influence of deposition paramters in pulsed laser deposition (PLD) on the phase purity and structural quality of the layers as well as on the charge carrier density and mobility in the BaSnO3 and LaInO3 layers. In cooperation with the section "Oxide & Fluoride" different oxide crystals are used as substrates for epitaxial deposition, since a reduction of the defect density in the layers shall be achieved by a smaller lattice mismatch.

Contact

Daniel Pfützenreuter

Ph. +49 30 6392 3043

Email

Piezo-/ferroelectric properties of strained (K,Na)NbO₃ thin films

Ferro- and piezoelectric oxide thin films play an eminent role in advancing emerging technologies like e.g. surface acoustic waves sensors with extremely high sensitivity, non-volatile memories, MEMS. The long-time market-dominating piezo-/ferroelectric materials have been lead-based oxides, which are toxic and thus their utilization has been restricted in many countries. Our mission is to explore the ferro-/piezoelectric properties of one of the most promising lead-free material systems (K,Na)NbO3 in thin film form and to provide the material for potential applications.

Growth of epitaxial films on lattice mismatched oxide substrates allows the incorporation of lattice strain and thus the engineering of their ferro- and piezoelectric properties (like Curie temperature, piezoelectric constants). This is achieved by a close cooperation with the Section “Oxides & Fluorides”. We perform epitaxial growth by pulsed laser deposition and as the only group worldwide by metal-organic vapor phase epitaxy. Film characterization by piezoresponse force microscopy reveals insights into ferroelectric domain formation as a function of the lattice strain.

Leonard von Helden, Laura Bogula, Pierre-Eymeric Janolin, Michael Hanke, Tobias Breuer, Martin Schmidbauer, Steffen Ganschow, and Jutta Schwarzkopf,
Huge impact of compressive strain on phase transition temperatures in epitaxial ferroelectric KxNa1-xNbO3 thin films
Appl. Phys. Lett. 114, 232905 (2019)
DOI: 10.1063/1.5094405

Dorothee Braun, Martin Schmidbauer, Michael Hanke and Jutta Schwarzkopf
Hierarchy and scaling behavior of multi-rank domain patterns in ferroelectric K0.9Na0.1NbO3 strained films
Nanotechnology 29, 015701 (2018)
DOI: 10.1088/1361-6528/aa98a4

Jutta Schwarzkopf, Dorothee Braun, Michael Hanke, Reinhard Uecker and Martin Schmidbauer
Strain engineering of ferroelectric domains in KxNa1-xNbO3 epitaxial layers
Front. Mater. 4, 26 (2017)
DOI: 10.3389/fmats.2017.00026

 

Contact

Dr. Jutta Schwarzkopf

Ph. +49 30 6392 3053

Email

„2D goes 3D” by Layer Transfer

A new paradigm to assemble crystalline materials is established by layer transfer, a method to built-up novel epitaxial heterostructures which cannot be grown by traditional methods due to incompatibility of lattice parameters, symmetry, or others. We are aiming for a comprehensive and flexible technical approach to facilitate the realization of various demands in basic and applied research, seeking synergies with local academic and industrial partners.

We are currently setting up a layer transfer station in HV-conditions with the goal of a fully remote-controlled transfer process. We will transfer exfoliated monolayers of 2D-crystals and epitaxial films up to 2”-wafers. In basic research, a special interest is in emergent phases such as strongly correlated electronic matter in 2D-heterostructures. In applied research, high performance systems can be realized by the combination of the best materials for the best function in a hybrid approach.

Hao Chen, Pinjia Zhou, Jiawei Liu, Jiabin Qiao, Barbaros Oezyilmaz, Jens Martin
Gate controlled valley polarizer in bilayer graphene
Nature Communications
DOI: 10.1038/s41467-020-15117-y

Contact

Dr. Jens Martin

Ph. +49 30 6392 2857

Email