Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session E28: Dopants and Defects in Semiconductors III: Complex OxidesFocus
|
Hide Abstracts |
Sponsoring Units: DMP FIAP DCOMP Chair: Matthew McCluskey, Washington State University Room: 291 |
Tuesday, March 14, 2017 8:00AM - 8:36AM |
E28.00001: The interaction of dopants and native point defects in functional complex oxides Invited Speaker: Leigh Weston Oxide semiconductors are often doped with heterovalent substitutional impurities, which modify the Fermi level and lead to the formation of charge-compensating native point defects. Using first-principles calculations, we demonstrate the interplay between doping and native defect formation in complex oxides, highlighting the potential for both positive and detrimental effects. As a first example, we study the proton-conducting complex oxide SrZrO$_3$ (SZO). In undoped SZO, the defect chemistry is dominated by oxygen vacancies ($V_\mathrm{O}$) and strontium vacancies ($V_\mathrm{Sr}$) [1], whose concentrations are constrained by charge neutrality. Upon acceptor doping with Sc or Y at the Zr site, the concentration of $V_\mathrm{O}$ can be increased, and the concentration of $V_\mathrm{Sr}$ can be reduced; we discuss how this promotes both proton solubility and diffusion. However, under certain growth conditions, Sc and Y will substitute at the Sr site and act as donors, with detrimental consequences for proton conductivity. The second example is the alkaline-earth stannates (ASnO$_3$; A = Ba, Sr, Ca), which are promising transparent conducting oxides. The stannates can be doped with La donors. High levels of $n$-type doping can be achieved in BaSnO$_3$; however, the achievable carrier concentrations in (Ba,Sr)SnO3 alloys are much lower [J. Vac. Sci. Technol. A 34, 050601 (2016)]. We investigate the origin of this $n$-type doping difficulty, finding that the formation energy of A-site cation vacancies becomes very low under $n$-type conditions; these vacancies act as charge-compensating acceptors, reducing the $n$-type conductivity. This effect is discussed in light of recent experimental results, and we provide guidelines for engineering the growth environment to achieve higher $n$-type doping. [Preview Abstract] |
Tuesday, March 14, 2017 8:36AM - 8:48AM |
E28.00002: $p$-doped BiFeO$_3$ - a survey of the periodic table Julian Gebhardt, Andrew Rappe We provide a comprehensive study of substitutional metal doping in multiferroic BiFeO$_{3}$ (BFO) by $ab~initio$ calculations. The study focuses on $p$-type doping, since, to date, no successful $p$-doped modification has been reported, impeding its use in electronic applications. Despite the resulting focus on M$^{+n<3}$ cations, we also discuss isovalent and aliovalent $n$ dopants. The resulting set of candidates spans the most part of the periodic table and we investigate the possibility and the effects on the electronic structure of substitutional doping in both A- (Bi) and B-site (Fe) for each dopant. We are able to establish trends and to identify suitable $p$ dopants in both possible doping sites. Furthermore, we extend our study in order to incorporate the effects of oxygen vacancies on the electronic structure. This is the most important structural defect in BFO as oxygen vacancies, which are present in most experimentally grown crystals, inherently lead to $n$ doping of the material. We find that the formation of oxygen vacancies depends on the oxidation state of the dopant but also deviations within groups of the same oxidation state are observed. This allows us to rank all $p$ dopants with respect to their tendency to limit oxygen vacancy formation. [Preview Abstract] |
Tuesday, March 14, 2017 8:48AM - 9:00AM |
E28.00003: High mobility La-doped BaSnO$_{\mathrm{3}}$ on non-perovskite MgO substrate Youjung Kim, Juyeon Shin, Young Mo Kim, Kookrin Char (Ba,La)SnO$_{\mathrm{3}}$ is a transparent perovskite oxide with high electron mobility and excellent oxygen stability. Field effect device with (Ba,La)SnO$_{\mathrm{3}}$ channel was reported to show good output characteristics on STO substrate. Here, we fabricated (Ba,La)SnO$_{\mathrm{3\thinspace }}$films and field effect devices with (Ba,La)SnO$_{\mathrm{3}}$ channel on non-perovskite MgO substrates, which are available in large size wafers. X-ray diffraction and transmission electron microscope (TEM) images of (Ba,La)SnO$_{\mathrm{3\thinspace }}$films on MgO substrates show that the films are epitaxial with many threading dislocations. (Ba,La)SnO$_{\mathrm{3}}$ exhibits the high mobility with 97.2 cm$^{\mathrm{2}}$/Vs at 2 {\%} La doping on top of 150 nm thick BaSnO$_{\mathrm{3}}$ buffer layer. Excellent carrier modulation was observed in field effect devices. FET performances on MgO substrates are slightly better than those on SrTiO$_{\mathrm{3}}$ substrates in spite of the higher dislocation density on MgO than on SrTiO$_{\mathrm{3}}$ substrates. These high mobility BaSnO$_{\mathrm{3}}$ thin films and transistors on MgO substrates will accelerate development for applications in high temperature and high power electronics. [Preview Abstract] |
Tuesday, March 14, 2017 9:00AM - 9:12AM |
E28.00004: Modulation doping at BaSnO$_{\mathbf{3}}${LaInO}$_{\mathbf{3}}$ Kookrin Char, Juyeon Shin, Young Mo Kim, Youjung Kim We recently reported on the conductance enhancement at the interface between two band insulators: LaInO$_{3}$ (LIO) and BaSnO$_{3}$ (BSO). These two-dimensional electron gas-like (2DEG) states at the LIO/Ba$_{1-x}$La$_{x}$SnO$_{3}$ (BLSO) polar interface display the stability, the controllability of the local carrier concentration, and the high electron mobility of BLSO. Search for the origin of enhanced conductance at the interface has been carried out, and one of the findings is that the doping level of BSO is a critical parameter for the polar charge contribution . We have also investigated a new modulated heterostructure by inserting an undoped BSO spacer layer at the LIO/BLSO interface. As increasing the thickness of the spacer layer, the carrier concentration and the mobility continually decreased. We attribute the results to the modified band bending as the thickness of the spacer layer varies and to the dislocation-limited transport. However, when we controlled the band bending by field effect, improved mobility was observed in these modulated heterostructures. This new modulated heterostructures of the LIO/BSO polar interface look promising not only for higher electron mobility devices but also for elucidating the mechanism of the 2DEG-like behavior. [Preview Abstract] |
Tuesday, March 14, 2017 9:12AM - 9:24AM |
E28.00005: P-type field effect transistor based on Na-doped BaSnO$_{\mathrm{3}}$ Yeaju Jang, Sungyun Hong, Jisung Park, Kookrin Char We fabricated field effect transistors (FET) based on the p-type Na-doped BaSnO$_{\mathrm{3}}$ (BNSO) channel layer. The properties of epitaxial BNSO channel layer were controlled by the doping rate. In order to modulate the p-type FET, we used amorphous HfO$_{\mathrm{x}}$ and epitaxial BaHfO$_{\mathrm{3}}$ (BHO) gate oxides, both of which have high dielectric constants. HfO$_{\mathrm{x}}$ was deposited by atomic-layer-deposition and BHO was epitaxially grown by pulsed laser deposition. The pulsed laser deposited SrRuO$_{\mathrm{3}}$ (SRO) was used as the source and the drain contacts. Indium-tin oxide and La-doped BaSnO$_{\mathrm{3}}$ were used as the gate electrodes on top of the HfO$_{\mathrm{x}}$ and the BHO gate oxides, respectively. We will analyze and present the performances of the BNSO field effect transistor such as the $I_{\mathrm{DS}}$-$V_{\mathrm{DS}}$, the $I_{\mathrm{DS}}$-$V_{\mathrm{GS}}$, the $I_{\mathrm{on}}$/$I_{\mathrm{off}}$ ratio, and the field effect mobility. [Preview Abstract] |
Tuesday, March 14, 2017 9:24AM - 9:36AM |
E28.00006: P-type hole mobility measurement in Na-doped BaSnO$_{\mathrm{\mathbf{3}}}$ Sungyun Hong, Yeaju Jang, Jisung Park, Kookrin Char P-type doping in oxide materials has been a difficult task because of the oxygen vacancies. Taking advantage of the excellent oxygen stability in BaSnO$_{\mathrm{3}}$ (BSO), we replaced Ba with Na in BSO to achieve p-type doping. Ba$_{\mathrm{1-x}}$Na$_{\mathrm{x}}$SnO$_{\mathrm{3}}$ (BNSO) films with varying dopant ratios were epitaxially grown by the pulsed laser deposition technique. We confirmed that the BNSO films were properly grown and determined their lattice constants with respect to the dopant ratio by x-ray diffraction. Due to the high resistance of the films at room temperature, we measured the transport properties of the BNSO films at temperatures ranging from 200 C to 400 C. Hall resistance measurements in a ± 5 kG magnetic field were performed to confirm that the films are indeed p-type. As the temperature increased, the hole carrier concentration of the films increased while the film resistance decreased. The hole mobility values, in the tens of cm$^{\mathrm{2}}$/Vsec range, were found to decrease with the temperature. We will present the complete doping rate and temperature dependence of the hole mobility and compare their behavior with those of n-type La-doped BSO. [Preview Abstract] |
Tuesday, March 14, 2017 9:36AM - 9:48AM |
E28.00007: Effects of La-doped BaSnO$_{\mathrm{\mathbf{3}}}$epitaxial electrode on the ferroelectric properties of BaTiO$_{\mathrm{\mathbf{3}}}$ Hahoon Lee, Young Mo Kim, Youjung Kim, Juyeon Shin, Kookrin Char In order to integrate the newly discovered high-mobility perovskite semiconductor BaSnO$_{\mathrm{3}}$ with a ferroelectric perovskite, we have grown epitaxial ferroelectric BaTiO$_{\mathrm{3}}$ (BTO) on top of the 4 {\%} La-doped BaSnO$_{\mathrm{3}}$ (BLSO). X-ray diffraction measurement suggests that the BTO film on top of BLSO electrode is tensilely strained due to the larger lattice constant of BLSO. An all epitaxial sandwich structure of BLSO/BTO/BLSO was fabricated in order to measure the ferroelectric properties of the BTO under tensile strain. The polarization-electric field (P-E) hysteresis curve will be discussed from the viewpoint of the tensile strain. In addition, the breakdown field will be measured to evaluate the potential of BTO for a gate oxide on top of BLSO. [Preview Abstract] |
Tuesday, March 14, 2017 9:48AM - 10:00AM |
E28.00008: Charge Transition of Oxygen Vacancies during Resistive Switching in Oxide-based Memristors Jihang Lee, Emmanouil Kioupakis, Wei Lu Resistive switching (RS) memristors find applications in non-volatile memory and neuromorphic computing. RS in oxide memristors originates from the redistribution of oxygen vacancies (V$_{\mathrm{O}}$s) to form conducting filaments of aggregated V$_{\mathrm{O}}$s. Since the ion migration is facilitated by an applied electric field, V$_{\mathrm{O}}$s in RS are considered positively charged (V$_{\mathrm{O}}^{\mathrm{2+}})$. We performed density function theory calculations to study the interactions between neutral and charged V$_{\mathrm{O}}$s in amorphous Ta$_{\mathrm{2}}$O$_{\mathrm{5}}$. The cohesive energy between charged V$_{\mathrm{O}}$s is strongly repulsive at short range, contradicting the experimentally observed high V$_{\mathrm{O}}$ concentration in filaments. On the other hand, neutral V$_{\mathrm{O}}$s exhibit a short-range attraction that facilitates aggregation, but their charge neutrality precludes interactions with an electric field. We propose a series of charge-transition processes at work during RS that enable V$_{\mathrm{O}}$ drift and aggregation. We experimentally support the proposed model with electrical measurements under visible-light illumination that induce charge transitions of V$_{\mathrm{O}}$s and enhance the programming and erasing processes. Our results provide microscopic understanding of the RS mechanism and the effect of light on ions/defects migration. [Preview Abstract] |
Tuesday, March 14, 2017 10:00AM - 10:12AM |
E28.00009: Structural, Electronic and Magnetic Properties of doped-LaPO4 Jan Andzelm, Mahesh Neupane, Gregory Garrett Lanthanum orthophosphates (LaPO4) are a very interesting class of host lattices of activator ions due to their high insolubility and high thermal stability, thus providing durable phosphors for optical applications. When substitutionally \quad doped with other rare-earth (RE) elements, RE-doped LaPO$_{\mathrm{4}}$ exhibits intriguing dopant-induced electronic and optical properties. Recent experimental studies have also achieved efficient optical luminescence in LaPO$_{\mathrm{4}}$ by varying RE concentration. Theoretical or computational study of the concentration dependent RE-doped LaPO$_{\mathrm{4\thinspace }}$so far has been limited. In this study, we present a detailed DFT-based theoretical study of RE-doped LaPO$_{\mathrm{4\thinspace }}$by varying the RE-dopant types and concentration from 25{\%} to 3{\%}. The importance of the inclusion of electron-electron interactions during the theoretical study of RE-doped LaPO$_{\mathrm{4}}$ systems will be highlighted by comparing the results from the local and hybrid functionals. Finally, an analysis on the effect of RE-dopant type and concentration on structural, electronic and magnetic properties of RE-doped LaPO$_{\mathrm{4}}$ systems will be presented, which might expand the applicability of these materials to other domains such as spintronics and magnonics. [Preview Abstract] |
Tuesday, March 14, 2017 10:12AM - 10:24AM |
E28.00010: Understanding Birnessite MnO$_2$: Effects of Small Polaron and Local Dipole Haowei Peng, John P. Perdew Birnessite MnO$_2$, usually with cations like K and Na intercalated between layers, is a class of potential cheap oxygen evolution reaction (OER) catalyst. Using hybrid density functional calculations, we investigate the electronic structures of the layered MnO$_2$ with the intercalated cation modelled as a defect. We found that an electron small polaron will form when an extra electron is doped in the pure MnO$_2$, turning a Mn(IV) to a Mn(III) with a singly occupied $e_g$ orbital located within the band gap, and the resulting small-polaron hopping conduction explains the observed low electric conductivity. The inter-layer doped K atom will donate one electron to one Mn ion as expected, and also contributes to a local dipole forming between K and the Mn(III), raising the electrostatic potential of the specific layer. With a certain spatial distribution of such local dipoles, the small-polaron $e_g$ states become comparable in energy with the global conduction band minimum, and charge transfer occurs. This further results in a singly or partially occupied $e_g$ orbital near the Fermi level, which has been regarded as a signal for an excellent OER catalyst. Our calculation helps understanding several experimental observations. [Preview Abstract] |
Tuesday, March 14, 2017 10:24AM - 10:36AM |
E28.00011: Interaction of small polarons and oxygen vacancies in CeO2 LU SUN, Ligen Wang, Anderson Janotti The properties that make cerium oxide (CeO2) a promising material for solid oxide fuel and electrochemical cells are closely related to the easy of oxygen vacancy formation and Ce4$+\leftrightarrow $Ce3$+$ conversion, i.e., small polaron formation. The effects of oxygen vacancy on the structure and electronic properties of CeO2 have been extensively studied from both experiment and theory, yet vacancy formation energy and parameters of the polaron-vacancy interaction vary over a wide range. Using first-principles calculations based on hybrid functional, we investigate the formation and migration of small polarons (Ce3$+)$ and their interaction with oxygen vacancies in CeO2, treating the small polaron and vacancy as independent entities. We compute the electron self-trapping energy (i.e., energy gain when forming a small polaron), the small-polaron migration barrier, vacancy formation and migration energies, and vacancy-polaron binding energies. We find that small polarons weakly bind to oxygen vacancies, providing a relatively small contribution to the activation energy barrier for the observed hopping electronic conductivity. The results are compared to previous calculations and discussed in the light of available experimental data. [Preview Abstract] |
Tuesday, March 14, 2017 10:36AM - 10:48AM |
E28.00012: Local structure of disordered Bi0.5K0.5TiO3 investigated by pair distribution function analysis and first principles calculations Bo Jiang, Andy Fitch, Tor Grande, Sverre Selbach We investigate the A-site cation ordering in the ferroelectric perovskite Bi0.5K0.5TiO3 (BKT) by Density Functional Theory (DFT) calculations and synchrotron X-ray total scattering. Using BKT as a prototypical lead-free ferroelectric perovskite with multiple A-site cations, we use a combination of theory and experiments to assess the energetics and resulting physical properties of cation ordering. Ten different cation orders in a 2x2x2 supercell were investigated by fitting real space pair distribution functions (PDF), and by calculating the relative energies with DFT. No particularly favourable cation order could be inferred from neither experiment nor theory. Ferroelectric polarization calculated by the Berry phase method and the point charge model yield values in the order of 50-100 $\mu$ C/cm2 for all possible cation orders, which is much larger than previously reported experimental values of about 30 $\mu$ C/cm2. This indicates that BKT does not possess long range A-site cation order. Reverse Monte Carlo (RMC) modelling of the total scattering data also support A-site disorder in BKT. Finally, the ferroelectric polarization calculated for structural models with local cation displacements in a pseudo-disordered A-site sublattice agrees with experimental observations. [Preview Abstract] |
Tuesday, March 14, 2017 10:48AM - 11:00AM |
E28.00013: Ab initio study of Ba$_{\mathrm{1-x}}$Sr$_{\mathrm{x}}$SnO$_{\mathrm{3}}$ and BaSn$_{\mathrm{1-x}}$M$_{\mathrm{x}}$O$_{\mathrm{3}}$ (M $=$ Bi, Pb) using the ACBN0 functional: structural, electronic and optical properties Haihang Wang, Priya Gopal, Marco Fornari, Stefano Curtarolo, Ichiro Takeuchi, Marco Buongiorno Nardelli Using the recently developed pseudo-hybrid Hubbard density functional ACBN0 [1], we have studied the structural, electronic and optical properties of Ba$_{\mathrm{1-x}}$Sr$_{\mathrm{x}}$SnO$_{\mathrm{3}}$ and BaSn$_{\mathrm{1-x}}$M$_{\mathrm{x}}$O$_{\mathrm{3}}$(M $=$ Bi, Pb). This study is motivated by recent experimental results which show that the solid solutions of BaSnO$_{\mathrm{3}}$ mixed with Bi, Sr or Pb remain transparent for a wide range of mixing ratio (up to 40 percent). While traditional DFT calculations on native BaSnO$_{\mathrm{3}}$ and BaBiO$_{\mathrm{3}}$ fail to open the gap (both systems result as semi-metals), thereby hindering the study of related materials, we demonstrate that using ACBN0, the band gaps open and are in good agreement with experiments. Particularly, in BaBiO$_{\mathrm{3}}$, we correctly reproduce the crystal structure instability caused by the well-known breathing and tilting modes of the oxygens, and the alternating ordering of Bi$^{\mathrm{3+\thinspace }}$and Bi$^{\mathrm{5+\thinspace \thinspace }}$ions. A detailed theoretical investigation of the alloyed systems together with some most recent experimental results will be discussed. [1] L.A. Agapito, S. Curtarolo, and M. Buongiorno Nardelli. \textit{Reformulation of DFT}$+$\textit{U as a Pseudohybrid Hubbard Density Functional for Accelerated Materials Discovery, }Phys. Rev. X \textbf{5, }011006 (2015). [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700