Transparente Halbleiter-Spintronik
Zusammenfassung der Projektergebnisse
During my Heisenberg scholarship, my working group "Nanospintronics" and I were able to deepen topics in solid state physics. This includes the understanding of the formation of stable bound magnetic polarons (BMP) in transparent semiconductors (magnetic ZnO), the understanding of the electroforming-free change in resistance in ternary oxides (BiFeO3 and YMnO3), the understanding of the wavelength-dependent magneto-optical coupling in magnetizable layers and the understanding of electrostatic interaction between smart carriers (Si with charge pattern) and electrically polarizable biomaterials. In order to understand the transport, magnetization, and magnetooptical properties of magnetic semiconductors with bound magnetic polarons (BMP), it is significant to describe the volume of magnetic semiconductor where BMP are formed. This volume can only be determined, if the radius of BMP is known. To the best of our knowledge, so far the static dielectric constant of magnetic semiconductors with BMP has not been determined from modelled impedance data. We confirmed the dielectric constant of ZnO (εr=8.64…9.97) and observed an increase of static dielectric constant εr in ZnMnO and in ZnCoO, namely εr=27.00 in ZnMnO with 5 at.% Mn, εr=33.87 in ZnMnO with 2 at.% Mn, εr=18.11 in ZnCoO with 5 at.% Co, and εr=22.01 in ZnCoO with 2 at.% Co. Furthermore, we have measured and modeled the temperature dependent magnetoconductance in ZnCoO and ZnMnO thin films with nominal concentrations of 5 at. %, 2 at. % and 0.1 at. %. We observed a temperature dependent anisotropy of interaction and localization effects as independent phenomena in magnetic ZnO. The modelling with the temperature dependence (LTh~T-0.5) for conducting surface is in good agreement with the Thouless diffusion length (LTh) proposed by the Nobel Prize winners David J. Thouless and J. Michael Kosterlitz in the 70s to describe transport in ultrathin films in the unordered phase. We observed and modelled tunability of the magnetoconductivity carried by a parallel combination of 2D layer conductance and 3D layer conductance in dependence on the species and concentration of magnetic ions in magnetic ZnO thin films. We have measured the Mueller matrix of multilayer samples with magnetizable layers by vector magnetooptical generalized ellipsometry (VMOGE) and modeled the magnetooptical dielectric tensor with the wavelength dependent magnetooptical coupling constant Q(λ). For ferromagnetic metal layers the magnetooptical dielectric tensor has been correlated with the results from spin density function theory calculations. It has been demonstrated how in a given spectral range the magnetooptical response of magneto-optical multilayer systems can be increased. Furthermore, we have developed an electroforming-free, bipolar memristor (BiFeO3) and an electroforming-free, unipolar memristor (YMnO3). The novel underlying switching mechanism in BiFeO3 which is the first memristor with analog data storage and information processing is the reconfiguration of the barrier height of the top electrode and of the bottom electrode. And the novel underlying switching mechanism in YMnO3 which is the first memristor which can switch not only between high and low resistance state but in the same time between capacitive and inductive state is the reconfiguration of vortex density. Finally, the surface-near electrostatic interaction between smart carriers (Si wafers with charge pattern) and electrically polarizable biomaterials has been shown to enable self-organized local attachement to areas of the surface of the smart carriers where the surface-near electrostatic interaction is attractive.
Projektbezogene Publikationen (Auswahl)
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Hysteretic anomalous Hall effect in a ferromagnetic, Mn-rich Ge:Mn nanonet. Applied Physics Letters, 100(1).
Bürger, Danilo; Zhou, Shengqiang; Höwler, Marcel; Ou, Xin; Kovacs, György J.; Reuther, Helfried; Mücklich, Arndt; Skorupa, Wolfgang; Helm, Manfred & Schmidt, Heidemarie
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Substrate effect on the resistive switching in BiFeO3 thin films. Journal of Applied Physics, 111(7).
Shuai, Yao; Ou, Xin; Wu, Chuangui; Zhang, Wanli; Zhou, Shengqiang; Bürger, Danilo; Reuther, Helfried; Slesazeck, Stefan; Mikolajick, Thomas; Helm, Manfred & Schmidt, Heidemarie
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Kelvin probe force microscopy for characterizing doped semiconductors for future sensor applications in nano- and biotechnology. Applied Surface Science, 281, 24-29.
Schmidt, Heidemarie; Habicht, Stefan; Feste, Sebastian; Müller, Anne-Dorothea & Schmidt, Oliver G.
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Persistent Current Reduction in Metal-Semiconductor FETs With a ZnCoO Channel in an External Magnetic Field. IEEE Electron Device Letters, 34(10), 1271-1273.
Kaspar, Tim; Fiedler, Jan; Skorupa, Ilona; Burger, Danilo; Mucklich, Arndt; Fritzsche, Monika; Schmidt, Oliver G. & Schmidt, Heidemarie
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Exploiting Memristive BiFeO3 Bilayer Structures for Compact Sequential Logics. Advanced Functional Materials, 24(22), 3357-3365.
You, Tiangui; Shuai, Yao; Luo, Wenbo; Du, Nan; Bürger, Danilo; Skorupa, Ilona; Hübner, René; Henker, Stephan; Mayr, Christian; Schüffny, René; Mikolajick, Thomas; Schmidt, Oliver G. & Schmidt, Heidemarie
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Transport in ZnCoO thin films with stable bound magnetic polarons. APL Materials, 2(7).
Kaspar, Tim; Fiedler, Jan; Skorupa, Ilona; Bürger, Danilo; Schmidt, Oliver G. & Schmidt, Heidemarie
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Engineering interface-type resistive switching in BiFeO3 thin film switches by Ti implantation of bottom electrodes. Scientific Reports, 5(1).
You, Tiangui; Ou, Xin; Niu, Gang; Bärwolf, Florian; Li, Guodong; Du, Nan; Bürger, Danilo; Skorupa, Ilona; Jia, Qi; Yu, Wenjie; Wang, Xi; Schmidt, Oliver G. & Schmidt, Heidemarie
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Single pairing spike-timing dependent plasticity in BiFeO3 memristors with a time window of 25 ms to 125 μs. Frontiers in Neuroscience, 9.
Du, Nan; Kiani, Mahdi; Mayr, Christian G.; You, Tiangui; Bürger, Danilo; Skorupa, Ilona; Schmidt, Oliver G. & Schmidt, Heidemarie
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An Energy‐Efficient, BiFeO3‐Coated Capacitive Switch with Integrated Memory and Demodulation Functions. Advanced Electronic Materials, 2(3).
You, Tiangui; Selvaraj, Laveen Prabhu; Zeng, Huizhong; Luo, Wenbo; Du, Nan; Bürger, Danilo; Skorupa, Ilona; Prucnal, Slawomir; Lawerenz, Alexander; Mikolajick, Thomas; Schmidt, Oliver G. & Schmidt, Heidemarie
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Photocapacitive light sensor based on metal-YMnO3-insulator-semiconductor structures. Applied Physics Letters, 108(5).
Bogusz, A.; Choudhary, O. S.; Skorupa, I.; Bürger, D.; Lawerenz, A.; Lei, Y.; Zeng, H.; Abendroth, B.; Stöcker, H.; Schmidt, O. G. & Schmidt, H.
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Thouless length and valley degeneracy factor of ZnMnO thin films with anisotropic, highly conductive surface layers. Journal of Applied Physics, 121(22).
Vegesna, Sahitya V.; Bürger, Danilo; Patra, Rajkumar; Abendroth, Barbara; Skorupa, Ilona; Schmidt, Oliver G. & Schmidt, Heidemarie
