PREDICTION OF THERMODYNAMIC STABILITY OF METAL/OXIDE INTERFACE

Size: px

Start display at page:

Download "PREDICTION OF THERMODYNAMIC STABILITY OF METAL/OXIDE INTERFACE"

Cory Fields
5 years ago
Views:

1 PREDICTION OF THERMODYNAMIC STABILITY OF METAL/OXIDE INTERFACE 14 Sept 010 Hong Mei Jin Ping Wu Institute of High Performance Computing Singapore

2 Computational Materials Science Department Michael Sullivan Deputy Program Manager Yu Zhigen EN Team Leader Daniel Cheong CC Team Leader Marco Klähn MM Team Leader Gan Chee Kwan MTS Team Leader

3 Oct008

4 Approaches for materials research Material s Method s Properti es Products Bulk Electronic Chemical Electronics Interface Classical Physical Energy Hybrid Nanostructures Continuum Structural Bio-medical Experiment interdisciplinary and multiscale nature...

5 Leading research.. Theory Semiconductor Physics Solution Chemistry Materials Informatics Materials Zinc Alloys & Zinc Oxides Ti/Zr Alloys & Ti/Zr Oxides Delafossite & Perovskite Applications Electronics Energy Bio-medical Devices

6 Materials Zinc alloy and Zinc oxide Metal-oxide interface Minor additives for Zn galvanizing Ontario- Singapore ETPL Cominco NUS IME, DSI, NTU Patent and licensing P-type ZnO ZnO based LED

7 Materials Ti/Zr alloy and Ti/Zr oxide Metal-oxide interface Bio-Ti alloys design High K ZrO Simtech IMRE IME NUS ICES NTU Rolls Royce NTU NYP U of Montreal Water splitting SOFC Bio-Zr alloys Nuclear energy

8 Introduction Density Functional Theory(DFT) calculation of Ni/ZrO, Cu/ZrO Empirical model for thermodynamic stability of Ni/ZrO, Cu/ZrO Model prediction for Au/TiO DFT verification of empirical prediction for Au/TiO Summary

9 Important in engineering applications: microelectronics packaging, optoelectronics structure composites and coatings of nuclear reactors heterogeneous catalysis, fuel cells A challenge to develop a fundamental Schottky Barrier formation mechanism understanding of the Well reported in TOFA010: O1, O47, O53, O7, P31, P38

10 Crystal structure of Ni (Cu, Au) and c-zro Ni (Cu, Au) Fm-3m Cubic ZrO Fm-3m Cubic

11 Calculation model (supercell approach) dark blue color: Ni(Cu), light blue color is Zr, red color is O atom, respectively

12 Calculation details DFT, planewave, pseudopotential method (vasp) Ultrasoft pseudopotential & GGA Cut off energy: 500 ev K points: 8x8x1 Since metal is less rigid, the lattice mismatch induced small in-plane strain was assigned to the metal Electronic energy was minimized using a mixture of the blocked Davidson and RMM-DIIS algorithm. Conjugate gradient method for ionic relaxation.

13 Work of adhesion energy E ad = ( E = σ tot m m + E + σ tot ZrO ZrO E γ tot m, ZrO ) / m, ZrO A where σ is the surface energy, A is interface area, γ is interfacial energy, it can be obtained from Gibbs free energy of the system: tot γ m, ZrO = Em ZrO N mµ m NZrµ Zr NOµ O + PV TS) / A (, where µ is the chemical potential, N is the number of the atoms in the interface system, V is volume and S is entropy. For typical working temperature and pressure, term PV and TS can be neglected. Further, µzro= µzr+µo. So the above equation becomes: tot bulk bulk γ m, ZrO = ( E m, ZrO NmE m N Zr EZrO ( No N Zr ) o / A µ for stoichiometric interface, the coefficient of µo will be zero, however, for non-stoichiometric interface, it will be a function of oxygen potential.

15 Calculated interfacial energy, surface energy and work of adhesion for more relatively stable stoichiometric interface of Ni(110)/ZrO(110) and Cu(110)/ZrO(110) surface energy (ev) interfacial energy (ev) Work of adhesion (J/m) Ni(110) Ni/ZrO Cu(110) Cu/ZrO ZrO(110) 0.09 Experiment results [ref] Ref: D. Sotiropoulou et al., Ref: J. Mater. Sci,8(1993)356, Ceramics International, 15(1989)01.

16 Summary: 1. In the intermediate range of oxygen partial pressures, (110)Ni/Cu- (110)ZrO is more stable. At extreme high or low oxygen partial pressure, non-stoichiometric interface could be more stable 3. The calculated adhesion energies are in agreement with experiment results Challenges: to replace the computing intensive DFT calculations by simple empirical equations!

17 Based on MacDonald and Eberhart [1], D.Chatain et al [] and Miedema s model[3], we define the interfacial energy and work of adhesion as following: γ m, MO x = H o in< M > 1 1 ( + A < o> H M A in < M > where Ho in <M1> and H M1 in M are the partial enthalpy of mixing. For Ho in <M1>, the following equation [4] was used: M ) (1) H o in f < M > 1. H < MO > For H M1 in M, we used the literature data from [3,5-7]. A is molar interface area which is defined at the next page. x 5 ( Jmol 1 O) [1] Trans.Metall.Soc. AIME, 33:51-517, [] Revue Phys. Appl. 3, , [3] Cohesion in metals. [4] Phys. Rev. B, V6(000):4707 [5] J. Alloys. Comp., 36(1996):36-4 [6] J. Alloys. Comp., 40(006):175 [7] Appl. Phys. Lett., 69(1996):1701

18 For molar interface area, it can be calculated as: for fcc lattice: 1 { 111} face : A = 4 3 Na 1 {110} face : A = Na 1 {100} face : A = Na for tetragonal lattice TiO: {111} face : A = 1 + c 1 1 {111} face : A = a + c 3 1 {110} face : A = Na c 4 1 {110} face : A = Na c {100} face : A = a cn a an an ( Ti / O ter min ate) ( O + Ti ter min ate ) ( O + Ti ter min ate) ( O ter min ate) where N is Avogradro s number, a,c are lattice parameters

19 Apply equation (1) on Ni/ZrO(110), Cu/ZrO(110) Ni/ ZrO(110) E (J/m) γni,zro (J/m) Work of Ni-O Ni-Zr total adhesion Ead(J/m) Ni(111) Ni(110) Ni(100) Cu/ ZrO(110) E (J/m) γcu,zro (J/m) Work of adhesion Ead (J/m) Cu-O Cu-Zr total Cu(111) Cu(110) Cu(100) * here work of adhesion was calculated by (where σ is surface energy of metal and oxide, respectively): E ad σ + σ = m ZrO γ

20 Predicted interfacial energy and work of adhesion of Au/TiO between different crystal orientation Au/TiO(110) O-terminate E (J/m) γau,tio (J/m) Work of adhesion (J/m) Au-O Au-Ti total Au(111) Au(110) Au(100) Au/TiO(110) O+Ti-terminate E (J/m) γ Au/TiO(J/m) Work of adhesion (J/m) Au-O Au-Ti total Au(111) Au(110) Au(100)

21 Au/TiO(111) O-terminate E (J/m) γau/tio (J/m) Work of adhesion (J/m) Au-O Au-Ti total Au(111) Au(110) Au(100) Au/TiO(111) E (J/m) γau/tio (J/m) Work of O+Titerminate Au-O Au-Ti adhesion (J/m) total Au(111) Au(110) Au(100)

Au/TiO(001) O-terminate E (J/m) γ Au/TiO(J/m) Work of adhesion (J/m) Au-O Au-Ti total Au(111) 0.455 0.5419 0.997 0.58 Au(110) 0.455 0.3318 0.7871 1.10 Au(100) 0.

22 Au/TiO(001) O-terminate E (J/m) γ Au/TiO(J/m) Work of adhesion (J/m) Au-O Au-Ti total Au(111) Au(110) Au(100) The order of work of adhesion: 110-Au-110-TiO (O-ter) 100-Au-110-TiO(O-ter) 110-Au-110-TiO (O+Ti-ter) 111-Au-110-TiO(O-ter) 100-Au-(O+Ti)-110-TiO

23 Different termination of Rutile-TiO(110) surface (a) Stoichiometric slab (b) non-stoichiometric slab O deficient Ti deficient

24 Interface structure 110-Au/110-TiO 110-Au/110-TiO 100-Au/110-TiO

26 Calculated surface, interfacial energy and work of adhesion(j/m) Au on (O- terminate 110- TiO surface σm σtio γau/tio Ead Au(100) Au(110) Au(111) Au on (O+Ti)- terminate 110-TiO surface σm σtio γau/tio Ead Au(100) Au(110) tot γ Au TiO = ( EAu, TiO N Auµ Au NTiµ Ti NOµ O + PV TS) / A, E ad = = ( E σ tot m Au + + E σ tot TiO TiO tot E Au, TiO ) / γ Au, TiO A

28 1. DFT calculations were carried out to investigate the interface stability and work of adhesion between Ni(Cu)/ZrO. The calculated work of adhesion are comparable with experiment.. An empirical equation was proposed to estimate the interfacial energy between metal and oxide. It was applied on Ni(Cu)/ZrO and reasonable agreement with experiment were obtained by comparing to the work of adhesion. 3. The empirical equation was extended to Au/TiO. The interfacial energy and the work of adhesion were estimated for different surface orientation between Au and TiO. 4. DFT calculation were further performed on Au/TiO to verify the empirical estimation results. Good agreement were obtained in terms of relative interface stability. The predicted and calculated results are also in agreement with experimental observations.

29 谢谢! Thank you

Binding energy of 2D materials using Quantum Monte Carlo

Quantum Monte Carlo in the Apuan Alps IX International Workshop, 26th July to 2nd August 2014 The Apuan Alps Centre for Physics @ TTI, Vallico Sotto, Tuscany, Italy Binding energy of 2D materials using