Study on ZnO( 0001) surface with synchrotron radiation angle2resolved photoelectron spectroscopy

Transcription

1 Vol. 37,No J OURNAL OF UNIVERSITY OF SCIENCE AND TECHNOLO GY OF CHINA May : (2007) 04 & ZnO( 0001) 3 1, 1, 1, 1, 2, 2 (1., ; 2., ) : (angle2resolved p hotoeletron spectroscopy,arpes) (f ull potential linearized augmented plane waves,fpl A PW) ZnO (0001). ARPES ZnO A,. A RPES KM. :ZnO (0001) ; ; ; ; :O582 ;O ;O :A Study on ZnO( 0001) surface with synchrotron radiation angle2resolved photoelectron spectroscopy XU Peng2shou 1, WU Yu2yu 1, ZOU Chong2wen 1, SUN Bai 1, YUAN Hong2tao 2, DU Xiao2long 2 (1. N ational S ynchrotron Radiation L aboratory, University of Science and Technology of China, Hef ei , China; 2. Beijing N ational L aboratory f or Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing , China) Abstract : Synchrotron radiation angle2resolved p hotoelectron spectroscopy ( ARPES) combined with f ull potential linearized augmented plane waves ( FPL A PW) calculatio n was performed to investigate valence band electronic struct ure and energy band dispersing of ZnO (0001). The energy band struct ure of ZnO bulk state along t he A direction was obtained by using ARPES wit h normal emission and two surface states were identified. The experimental result s agree well wit h t heoretical calculatio n. The 2D energy band dispersing of ZnO surface states along t he KM direction were obtained by using ARPES with off2 normal emissio n. Key words : ZnO (0001) ; synchrotron radiation ; angle resolved p hotoelectron spectroscopy ; f ull potential linearized augmented plane waves ; energy band st ruct ure 0 ZnO 2,, 3137 ev, 60 mev., [1 3 ]. ZnO 3 : ; : : ( , , ). : ( ),,1947,. :. E2mail : edu. cn ; Tel :

2 425 ZnO (0001) 561 ZnO, ZnO. ZnO [4,5 ], ZnO ( 0001 ), ZnO (0001).., MB E ( molecular beam epitaxy) ZnO (0001), ( density f unction t heory,df T) ( f ull potential linearized augmented plane waves, FPL A PW) [6 ],. 1 1 ZnO( 0001) ( 1 1) LEED ( 139 ev) Fig. 1 LEED pattern of clean ZnO( 0001)2( 1 1) ( electron energy E = 139 ev). V G. 22 ev 50 ev ( 1 ev). (ARU PS10), ( PES),, ( A ES) (L EED) ( R H EED) (MB E), ev,. ( E/ E) , [ 7 ]. ZnO MB E c [8 ]. 5 min,,. ( Pa) min. X ( XPS), Zn O, C. L EED (1 1), 1.. A RPES., 45,, 25 ev,. 0 ( ) 60 ( 2 ). WIEN2 K FPL A PW ZnO., Kohn2Sham,. FPL A PW, ( interstitial region, IR) Muffin2 Tin (M T).. M T l = 10, lns = 4. Rmin Kmax = 8, Rmin M T, Kmax. Perdew [ 9 ] ( generalized gradient approximation, GGA). Zn O M T , M T. Monkorst2Pack [10 ] k.. ZnO a = nm,, c = nm,

3 mry, FPL A PW ZnO, 2 (a) (b). 2 (c), 22 ev, ( VBM). 2, O 2p, ev ev Zn 3d,,., Zn 3d - 8 ev, 3 ev ; [ 11 ]., GaN Ga 3d,.,, K = 1 h, h ; EB ; V 0 2 m ( h - EB - + V 0 ), ;, Muffin2Tin, ev,. ZnO, a = nm,c = nm, A 6 nm FPL A PW A, (a) ZnO ; (b) ZnO (c), h = 22 ev 2 ZnO Fig. 2 Structures of bulk energy band and valence band of ZnO 2. 2 ZnO,. 22 ev 50 ev ( 1 ev)., K = 0, [ 0001 ] K, ZnO A. 3 ZnO( 0001) Fig. 3 ARPES with normal emission of ZnO( 0001) 3, ev S1-714 ev S2, S1 S2,, S1 S ev - 11 ev,

4 425 ZnO (0001) 563, k k = 2 m Ekin sin,, Ekin ;. 4 ZnO A Fig. 4 The energy band structure of ZnO bulk state along the A direction S1 S2,. 25 ev,. 0 ( ) 60 ( 2 ). ZnO (0001) 5, KM., S1 S2 KM. 6. S1 S2. 7 KM, S1, S2,. 7, S1 S2, k,., Ivanov [12 ]. ZnO, KM,. S1 O O 2p p2p, S2 (back2bonding) Zn 4s2O 2p, 5 ZnO( 0001) Fig. 5 Surface Brillouin zone of ZnO( 0001) 6 ( h = 25 ev) Fig. 6 ARPES data with off2normal emission ( h = 25 ev)

5 S1 S2 7 KM Fig. 7 2D energy band dispersing of surface Brillouin zone along KM direction. 3 (0001) ZnO,XPS L EED ZnO (0001). ARPES FPL A PW. ARPES ZnO A,., KM. ( References) [ 1 ] Ellmer K. Resistivity of polycrystalline zinc oxide films : Current status and physical limit [ J ]. J Phys. D : Appl. Phys., 2001, 34 : [ 2 ] Pearton S J, Norton D P, Ip K, et al. Recent progress in processing and properties of ZnO[J ]. Prog. Mater. Sci., 2005, 50 : [ 3 ] Look D C. Recent advances in ZnO materials and devices[j ]. Mater. Sci. Eng. B, 2001, 80 : [ 4 ] Chelikowsky J R. An oxygen pseudopotential : Application to the electronic structure of ZnO[J ]. Solid State Comm., 1977, 22 : [ 5 ] Girard R T, Tjernberg O, Chiaia G. Electronic structure of ZnO ( 0001 ) studied by angle2resolved photoelectron spectroscopy[j ]. Surf. Sci., 1997, 373 : [ 6 ] Blaha P, Schwarz K, Madsen G K H, et al. WIEN2k, an Augmented Plane Wave + Local Orbitals Program for Calculating Crystal Properties [ M ]. Austria : Techn. University Wien, [ 7 ] Zou C W, Sun B, Zhang W H, et al. Commissioning of a new beamline and station for ARPES at NSRL [J ]. Nucl. Instrum. Meth. A, 2005, 548 : [ 8 ] Mei Z X, Wang Y, Du X L, et al. Controlled growth of O2polar ZnO epitaxial film by oxygen radical preconditioning of sapphire substrate [ J ]. J Appl. Phys., 2004, 96 : [ 9 ] Perdew J P, Burke K, Ernzerhof M, et al. Generalized gradient approximation made simple [ J ]. Phys. Rev. Lett., 1996, 77 : [ 10 ] Monkhorst H J. Special point s for Brillouin2zone integrations[ J ]. Phys. Rev. B., 1976, 13 : [ 11 ] Lambrecht W R L, Segall B. X2ray photoelectron spectroscopy and theory of the valence band and semicore Ga 3d states in GaN [ J ]. Phys. Rev. B., 1994, 50 : [12 ] Ivanov I, Pollmann J. Electronic structure of ideal and relaxed surfaces of ZnO : A prototype ionic wurtzite semiconductor and its surface properties [ J ]. Phys. Rev. B., 1981, 24 :