Electron Emission Energy Barriers and Stability of Sc2O3 with Adsorbed Ba and Ba–O

In this study we employ density functional theory (DFT) methods to investigate the surface energy barrier for electron emission (surface barrier) and thermodynamic stability of Ba and Ba–O species adsorption (relative to formation of bulk BaO) under conditions of high temperature (approximately 1200 K) and low pressure (approximately 10–10 Torr) on the low-index surfaces of bixbyite Sc2O3. We employ both the standard generalized gradient approximation (GGA) and the hybrid HSE functional to calculate accurate surface barriers from relaxed GGA structures. The role of Ba in lowering the cathode surface barrier is investigated via adsorption of atomic Ba and Ba–O dimers, where the highest simulated dimer coverage corresponds to a single-monolayer film of rocksalt BaO. The change of the surface barrier of a semiconductor due to adsorption of surface species is decomposed into two parts: a surface dipole component and a doping component. The dipole component is the result of charge rearrangement at the surface ...

[1]  I. Brodie,et al.  A general phenomenological model for work function , 2014 .

[2]  Wei Liu,et al.  DC Emission Characteristic of Nanosized-Scandia-Doped Impregnated Dispenser Cathodes , 2014, IEEE Transactions on Electron Devices.

[3]  Ivor Brodie,et al.  Scandate Dispenser Cathodes With Sharp Transition and Their Application in Microwave Tubes , 2014, IEEE Transactions on Electron Devices.

[4]  K. Butler,et al.  Prediction of electron energies in metal oxides. , 2014, Accounts of chemical research.

[5]  R. Gordon,et al.  Atomic layer deposition of Sc2O3 for passivating AlGaN/GaN high electron mobility transistor devices , 2012 .

[6]  John H. Booske,et al.  Intrinsic defects and conduction characteristics of Sc 2 O 3 in thermionic cathode systems , 2012, 1607.02080.

[7]  R. J. Temkin,et al.  Vacuum Electronic High Power Terahertz Sources , 2011, IEEE Transactions on Terahertz Science and Technology.

[8]  Yiman Wang,et al.  Emission mechanism of high current density scandia-doped dispenser cathodes , 2011 .

[9]  Gianfranco Pacchioni,et al.  Density functional theory study of TiO 2 /Ag interfaces and their role in memristor devices , 2011 .

[10]  M. Kordesch,et al.  Model scandate cathodes investigated by thermionic-emission microscopy , 2011 .

[11]  I. Brodie A New Model for the Mechanism of Operation of Scandate and Refractory Oxide Cathodes , 2011, IEEE Transactions on Electron Devices.

[12]  Aron Walsh,et al.  Structure, stability and work functions of the low index surfaces of pure indium oxide and Sn-doped indium oxide (ITO) from density functional theory , 2010 .

[13]  T. Butz,et al.  Electronic and structural properties, and hyperfine interactions at Sc sites in the semiconductor Sc 2 O 3 : TDPAC and ab initio study , 2010 .

[14]  D. Morgan,et al.  Ab initio investigation of barium-scandium-oxygen coatings on tungsten for electron emitting cathodes , 2010 .

[15]  Dane Morgan,et al.  Ab initio energetics of LaBO3(001) (B=Mn, Fe, Co, and Ni) for solid oxide fuel cell cathodes , 2009 .

[16]  Y. Takai,et al.  Change in work function during phase transition of Sc–O/W(1 0 0) system at high temperatures , 2009 .

[17]  Yanming Ma,et al.  High-pressure structural transitions of Sc2O3 by X-ray diffraction, Raman spectra, and ab initio calculations. , 2009, Inorganic chemistry.

[18]  D. Morgan,et al.  Ab initio investigation of the surface properties of dispenser B-type and scandate thermionic emission cathodes , 2009 .

[19]  D. Sholl,et al.  Density Functional Theory: A Practical Introduction , 2009 .

[20]  W. Liu,et al.  Correlation Between Emission Behavior and Surface Features of Scandate Cathodes , 2009, IEEE Transactions on Electron Devices.

[21]  D. Sholl,et al.  What is Density Functional Theory , 2009 .

[22]  G. Pacchioni,et al.  Work function changes induced by deposition of ultrathin dielectric films on metals: A theoretical analysis , 2008 .

[23]  B. Delley,et al.  Surface structure of Sn-doped In2O3 (111) thin films by STM , 2008 .

[24]  John H. Booske,et al.  Plasma physics and related challenges of millimeter-wave-to-terahertz and high power microwave generationa) , 2008 .

[25]  L. Giordano,et al.  Prediction of uncompensated polarity in ultrathin films. , 2007, Physical review letters.

[26]  L. Giordano,et al.  Charge transfers at metal/oxide interfaces: a DFT study of formation of Kδ+ and Auδ− species on MgO/Ag(100) ultra-thin films from deposition of neutral atoms , 2006 .

[27]  L. Giordano,et al.  Tuning the surface metal work function by deposition of ultrathin oxide films: Density functional calculations , 2006 .

[28]  J. P. Mannaerts,et al.  Structure of Sc2O3 films epitaxially grown on α-Al2O3 (0001) , 2006 .

[29]  Yiman Wang,et al.  Characteristics of scandate-impregnated cathodes with sub-micron scandia-doped matrices , 2005 .

[30]  J. Kwo,et al.  Thin single-crystal Sc2O3 films epitaxially grown on Si (111)-structure and electrical properties , 2005 .

[31]  T. Tsujita,et al.  Surface atoms in Sc–O/W(1 0 0) system as Schottky emitter at high temperature , 2003 .

[32]  G. Scuseria,et al.  Hybrid functionals based on a screened Coulomb potential , 2003 .

[33]  Rishabh Mehandru,et al.  Gadolinium Oxide and Scandium Oxide: Gate Dielectrics for GaN MOSFETs , 2001 .

[34]  A. Emeline,et al.  Photostimulated Generation of Defects and Surface Reactions on a Series of Wide Band Gap Metal-Oxide Solids , 1999 .

[35]  G. Briggs,et al.  An STM study of the UO2(001) surface , 1999 .

[36]  G. Kresse,et al.  From ultrasoft pseudopotentials to the projector augmented-wave method , 1999 .

[37]  P. A. Duine,et al.  A model system for scandate cathodes , 1997 .

[38]  A. Ritz,et al.  Emission properties of top-layer scandate cathodes prepared by LAD , 1997 .

[39]  Wang,et al.  Generalized gradient approximation for the exchange-correlation hole of a many-electron system. , 1996, Physical review. B, Condensed matter.

[40]  Kresse,et al.  Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. , 1996, Physical review. B, Condensed matter.

[41]  A. S. Gilmour Principles of Traveling Wave Tubes , 1994 .

[42]  R. S. Raju,et al.  Characterization of an impregnated scandate cathode using a semiconductor model , 1994 .

[43]  S. C. Parker,et al.  Computer simulation of the crystal morphology of NiO , 1993 .

[44]  Wang,et al.  Correlation hole of the spin-polarized electron gas, with exact small-wave-vector and high-density scaling. , 1991, Physical review. B, Condensed matter.

[45]  P. Wolf,et al.  Surface extended x‐ray absorption fine structure study of surface BaO layers on tungsten surfaces , 1988 .

[46]  A. Shih,et al.  Interatomic Auger analysis of the oxidation of thin Ba films: II. Applications to impregnated cathodes , 1983 .

[47]  Sharon Hagopian,et al.  Neutral three-pion resonance production in 15-GeV/ c π + -deuteron collisions , 1980 .

[48]  P. W. Tasker,et al.  The stability of ionic crystal surfaces , 1979 .

[49]  Ralph Forman,et al.  A proposed physical model for the impregnated tungsten cathode based on Auger surface studies of the Ba-O-W system , 1979 .

[50]  R. Forman Surface studies of barium and barium oxide on tungsten and its application to understanding the mechanism of operation of an impregnated tungsten cathode , 1976 .

[51]  H. Monkhorst,et al.  SPECIAL POINTS FOR BRILLOUIN-ZONE INTEGRATIONS , 1976 .

[52]  H. H. Tippins Absorption edge spectrum of scandium oxide , 1966 .

[53]  R. Levi,et al.  Improved ``Impregnated Cathode'' , 1955 .

[54]  G. Mahlman Work Functions and Conductivity of Oxide‐Coated Cathodes , 1949 .

[55]  A. F.,et al.  Thermionic Emission , 1936, Nature.

[56]  S. Dushman Electron Emission from Metals as a Function of Temperature; Added Note , 1923 .

[57]  O. Richardson LXVII. The distribution of the molecules of gas in a field of force, with applications to the theory of electrons , 1914 .