Nanofabrication

Semiconducting oxides

Oxides are among the materials with the widest tunability of physical properties. Spanning insulators, semiconductors, metallic conductors and superconductors, magnetic materials, ferro-/antiferro- and other dielectrics, oxides are a materials class with high potential for a new generation of electronic devices for energy and sensing applications.

Traditionally, oxides have been synthesized by pulsed laser deposition or sputtering, which both have drawbacks in terms of material quality. A higher material quality can be achieved by molecular beam epitaxy (MBE), which is the growth method used by us.

Our research aims at exploring the properties of semiconducting oxides at the materials limit, equally taking into account the understanding of the growth thermodynamics and kinetics as well as the materials application perspective. Providing samples for (international) collaborations is an important part of our scientific culture. To date, our materials portfolio comprises the n-type oxides (Ga,In,Al)₂O₃, SnO₂, the perovskites BaSnO₃ and LaInO₃, as well as the p-type oxides SnO and (the antiferromagnet) NiO. Out of these SnO₂, NiO, and In₂O₃ are frequently used in conductometric gas sensing—an application whose fundamental investigation together with external collaborators greatly benefits from our well-defined samples. Energy-efficient power electronics as well as solar-blind UV sensing are further important applications, both of which are foreseen to profit tremendously from the ultra-wide bandgap semiconductor Ga₂O₃ and its solid solutions with In₂O₃ and Al₂O₃.

Embedded in the Berlin-based Leibniz ScienceCampus „Growth and fundamentals of oxides for electronic applications“ (GraFOx), led by PDI, our activities are currently divided into the following projects:

MBE growth kinetics and doping of (Ga,Al)₂O₃ for power electronics
MBE growth and doping of p-type oxides
MBE of (In_1-xGa_x)₂O₃ for gas sensing applications
MBE of LaInO₃/BaSnO₃ heterostructures for electronic applications (funding in Leibniz competition “BaSnO₃-based heterostructures for electronic applications”)

Selected Publications

8	Author	P. Mazzolini , A. Falkenstein , C. Wouters , R. Schewski , T. Markurt , Z. Galazka , M. Martin , M. Albrecht , O. Bierwagen
	Title	Substrate-orientation dependence of β-Ga2O3 (100), (010), (001), and (ˉ201) homoepitaxy by indium-mediated metal-exchange catalyzed molecular beam epitaxy (MEXCAT-MBE)
	Source	APL Mater. , 8 , 011107 ( 2020 )
DOI : 10.1063/1.5135772 \| Download: PDF \| 3156 Cite : Bibtex RIS @article{ author = { P. Mazzolini and A. Falkenstein and C. Wouters and R. Schewski and T. Markurt and Z. Galazka and M. Martin and M. Albrecht and O. Bierwagen }, title = { Substrate-orientation dependence of β-Ga2O3 (100), (010), (001), and (ˉ201) homoepitaxy by indium-mediated metal-exchange catalyzed molecular beam epitaxy (MEXCAT-MBE) }, journal = { APL Materials }, volume = { 8 }, year = { 2020 }, pages = { 011107 } } P. Mazzolini, A. Falkenstein, C. Wouters, R. Schewski, T. Markurt, Z. Galazka, M. Martin, M. Albrecht, and O. Bierwagen TY - JOUR AU - P. Mazzolini AU - A. Falkenstein AU - C. Wouters AU - R. Schewski AU - T. Markurt AU - Z. Galazka AU - M. Martin AU - M. Albrecht AU - O. Bierwagen TI - Substrate-orientation dependence of β-Ga2O3 (100), (010), (001), and (ˉ201) homoepitaxy by indium-mediated metal-exchange catalyzed molecular beam epitaxy (MEXCAT-MBE) JF - APL Materials JA - APL Mater. J1 - APLM VL - 8 SP - 011107 PY - 2020/01/10

7	Author	G. Hoffmann , M. Budde , P. Mazzolini , O. Bierwagen
	Title	Efficient suboxide sources in oxide molecular beam epitaxy using mixed metal + oxide charges: The examples of SnO and Ga2O
	Source	APL Mater. , 8 , 031110 ( 2020 )
DOI : 10.1063/1.5134444 \| Download: PDF \| 3152 Cite : Bibtex RIS @article{ author = { G. Hoffmann and M. Budde and P. Mazzolini and O. Bierwagen }, title = { Efficient suboxide sources in oxide molecular beam epitaxy using mixed metal + oxide charges: The examples of SnO and Ga2O }, journal = { APL Materials }, volume = { 8 }, year = { 2020 }, pages = { 031110 } } G. Hoffmann, M. Budde, P. Mazzolini, and O. Bierwagen TY - JOUR AU - G. Hoffmann AU - M. Budde AU - P. Mazzolini AU - O. Bierwagen TI - Efficient suboxide sources in oxide molecular beam epitaxy using mixed metal + oxide charges: The examples of SnO and Ga2O JF - APL Materials JA - APL Mater. J1 - APLM VL - 8 SP - 031110 PY - 2020/03/12

6	Author	C. Golz , Z. Galazka , J. Lähnemann , V. Hortelano , F. Hatami , W.T. Masselink , O. Bierwagen
	Title	The electrical conductivity tensor of beta-Ga2O3 analyzed by van der Pauw measurements: Inherent anisotropy, off-diagonal element, and the impact of grain boundaries
	Source	Phys. Rev. Mater. , 3 , 124604 ( 2019 )
DOI : 10.1103/physrevmaterials.3.124604 \| Download arXiv: \| 3121 Cite : Bibtex RIS @article{ author = { C. Golz and Z. Galazka and J. Lähnemann and V. Hortelano and F. Hatami and W.T. Masselink and O. Bierwagen }, title = { The electrical conductivity tensor of beta-Ga2O3 analyzed by van der Pauw measurements: Inherent anisotropy, off-diagonal element, and the impact of grain boundaries }, journal = { Physical Review Materials }, volume = { 3 }, year = { 2019 }, pages = { 124604 } } C. Golz, Z. Galazka, J. Lähnemann, V. Hortelano, F. Hatami, W.T. Masselink, and O. Bierwagen TY - JOUR AU - C. Golz AU - Z. Galazka AU - J. Lähnemann AU - V. Hortelano AU - F. Hatami AU - W.T. Masselink AU - O. Bierwagen TI - The electrical conductivity tensor of beta-Ga2O3 analyzed by van der Pauw measurements: Inherent anisotropy, off-diagonal element, and the impact of grain boundaries JF - Physical Review Materials JA - Phys. Rev. Mater. J1 - VL - 3 SP - 124604 PY - 2019/12/27

5	Author	C.E. Simion , F. Schipani , A. Papadogianni , A. Stanoiu , M. Budde , A. Oprea , U. Weimar , O. Bierwagen , N. Barsan
	Title	Conductance Model for Single-Crystalline/Compact Metal Oxide Gas Sensing Layers in the Non-Degenerate Limit: Example of Epitaxial SnO2(101)
	Source	ACS Sens. , 4 , 2420 ( 2019 )
DOI : 10.1021/acssensors.9b01018 \| 3119 Cite : Bibtex RIS @article{ author = { C.E. Simion and F. Schipani and A. Papadogianni and A. Stanoiu and M. Budde and A. Oprea and U. Weimar and O. Bierwagen and N. Barsan }, title = { Conductance Model for Single-Crystalline/Compact Metal Oxide Gas Sensing Layers in the Non-Degenerate Limit: Example of Epitaxial SnO2(101) }, journal = { ACS Sensors }, volume = { 4 }, year = { 2019 }, pages = { 2420 } } C.E. Simion, F. Schipani, A. Papadogianni, A. Stanoiu, M. Budde, A. Oprea, U. Weimar, O. Bierwagen, and N. Barsan TY - JOUR AU - C.E. Simion AU - F. Schipani AU - A. Papadogianni AU - A. Stanoiu AU - M. Budde AU - A. Oprea AU - U. Weimar AU - O. Bierwagen AU - N. Barsan TI - Conductance Model for Single-Crystalline/Compact Metal Oxide Gas Sensing Layers in the Non-Degenerate Limit: Example of Epitaxial SnO2(101) JF - ACS Sensors JA - ACS Sens. J1 - VL - 4 SP - 2420 PY - 2019/08/15

4	Author	M. Budde , C. Tschammer , P. Franz , J. Feldl , M. Ramsteiner , R. Goldhahn , M. Feneberg , N. Barsan , A. Oprea , O. Bierwagen
	Title	Structural, optical, and electrical properties of unintentionally doped NiO layers grown on MgO by plasma-assisted molecular beam epitaxy
	Source	J. Appl. Phys. , 123 , 195301 ( 2018 )
DOI : 10.1063/1.5026738 \| Download: PDF \| 3016 Cite : Bibtex RIS @article{ author = { M. Budde and C. Tschammer and P. Franz and J. Feldl and M. Ramsteiner and R. Goldhahn and M. Feneberg and N. Barsan and A. Oprea and O. Bierwagen }, title = { Structural, optical, and electrical properties of unintentionally doped NiO layers grown on MgO by plasma-assisted molecular beam epitaxy }, journal = { Journal of Applied Physics }, volume = { 123 }, year = { 2018 }, pages = { 195301 } } M. Budde, C. Tschammer, P. Franz, J. Feldl, M. Ramsteiner, R. Goldhahn, M. Feneberg, N. Barsan, A. Oprea, and O. Bierwagen TY - JOUR AU - M. Budde AU - C. Tschammer AU - P. Franz AU - J. Feldl AU - M. Ramsteiner AU - R. Goldhahn AU - M. Feneberg AU - N. Barsan AU - A. Oprea AU - O. Bierwagen TI - Structural, optical, and electrical properties of unintentionally doped NiO layers grown on MgO by plasma-assisted molecular beam epitaxy JF - Journal of Applied Physics JA - J. Appl. Phys. J1 - JAP VL - 123 SP - 195301 PY - 2018/05/15

3	Author	Z. Cheng , M. Hanke , P. Vogt , O. Bierwagen , A. Trampert
	Title	Phase formation and strain relaxation of Ga2O3 on various sapphire orientations as studied by synchrotron-based x-ray diffraction
	Source	Appl. Phys. Lett. , 111 , 162104 ( 2017 )
DOI : 10.1063/1.4998804 \| Download: PDF \| 2948 Cite : Bibtex RIS @article{ author = { Z. Cheng and M. Hanke and P. Vogt and O. Bierwagen and A. Trampert }, title = { Phase formation and strain relaxation of Ga2O3 on various sapphire orientations as studied by synchrotron-based x-ray diffraction }, journal = { Applied Physics Letters }, volume = { 111 }, year = { 2017 }, pages = { 162104 } } Z. Cheng, M. Hanke, P. Vogt, O. Bierwagen, and A. Trampert TY - JOUR AU - Z. Cheng AU - M. Hanke AU - P. Vogt AU - O. Bierwagen AU - A. Trampert TI - Phase formation and strain relaxation of Ga2O3 on various sapphire orientations as studied by synchrotron-based x-ray diffraction JF - Applied Physics Letters JA - Appl. Phys. Lett. J1 - APL VL - 111 SP - 162104 PY - 2017/10/16

2	Author	P. Vogt , O. Brandt , H. Riechert , J. Lähnemann , O. Bierwagen
	Title	Metal-exchange catalysis in the growth of sesquioxides: towards heterostructures of transparent oxide semiconductors
	Source	Phys. Rev. Lett. , 119 , 196001 ( 2017 )
DOI : 10.1103/PhysRevLett.119.196001 \| Download: PDF \| 2925 Cite : Bibtex RIS @article{ author = { P. Vogt and O. Brandt and H. Riechert and J. Lähnemann and O. Bierwagen }, title = { Metal-exchange catalysis in the growth of sesquioxides: towards heterostructures of transparent oxide semiconductors }, journal = { Physical Review Letters }, volume = { 119 }, year = { 2017 }, pages = { 196001 } } P. Vogt, O. Brandt, H. Riechert, J. Lähnemann, and O. Bierwagen TY - JOUR AU - P. Vogt AU - O. Brandt AU - H. Riechert AU - J. Lähnemann AU - O. Bierwagen TI - Metal-exchange catalysis in the growth of sesquioxides: towards heterostructures of transparent oxide semiconductors JF - Physical Review Letters JA - Phys. Rev. Lett. J1 - PRL VL - 119 SP - 196001 PY - 2017/11/07

1	Author	J. Rombach , A. Papadogianni , M. Mischo , V. Cimalla , L. Kirste , O. Ambacher , T. Berthold , S. Krischok , M. Himmerlich , Sören Selve , O. Bierwagen
	Title	The role of surface electron accumulation and bulk doping for gas-sensing explored with single-crystalline In2O3 thin films
	Source	Sens. Actuators B Chem. , 236 , 909 ( 2016 )
DOI : 10.1016/j.snb.2016.03.079 \| 2784 Cite : Bibtex RIS @article{ author = { J. Rombach and A. Papadogianni and M. Mischo and V. Cimalla and L. Kirste and O. Ambacher and T. Berthold and S. Krischok and M. Himmerlich and Sören Selve and O. Bierwagen }, title = { The role of surface electron accumulation and bulk doping for gas-sensing explored with single-crystalline In2O3 thin films }, journal = { Sensors & Actuators B }, volume = { 236 }, year = { 2016 }, pages = { 909 } } J. Rombach, A. Papadogianni, M. Mischo, V. Cimalla, L. Kirste, O. Ambacher, T. Berthold, S. Krischok, M. Himmerlich, Sören Selve, and O. Bierwagen TY - JOUR AU - J. Rombach AU - A. Papadogianni AU - M. Mischo AU - V. Cimalla AU - L. Kirste AU - O. Ambacher AU - T. Berthold AU - S. Krischok AU - M. Himmerlich AU - Sören Selve AU - O. Bierwagen TI - The role of surface electron accumulation and bulk doping for gas-sensing explored with single-crystalline In2O3 thin films JF - Sensors & Actuators B JA - Sens. Actuators B Chem. J1 - VL - 236 SP - 909 PY - 2016/03/18