(Color online) Ball-and-stick models of relaxed ZnO/CdTe interface structures (2 × 2 × 1 supercells).
(Color online) Calculated ZnO/CdTe valence band offset via various methods for the lowest-energy Cd/O(4) geometry described in the text. Values for the “natural” band offset (Ref. 12 ) and experimental determination (average value, this work) are also presented. Inset: schematic of the calculated band alignment utilizing HSE06+U.
(Color online) Models of ZnO/CdTe interfaces modified to remove charge-transfer metallization.
(Color online) XPS core level spectra of Cd 3d 5/2 and Te 3d 5/2 from the as-received CdTe substrate. Spectra were collected at photoelectron takeoff angles of 90° and 12°. Fitted peak positions for spectra collected at 90° are given.
(Color online) XPS heterojunction valence band spectra (symbols) for ZnO/CdTe heterojunctions after exposure to the oxygen plasma for 10 min. The experimental heterojunction band offset (ΔE VBM) is given. Also shown is the sum (thick line) of experimental spectra from pure, bulk-like ZnO (dashed line), and bulk CdTe (thin line), which have been appropriately weighted and shifted as described in the text.
(Color online) GIXRD pattern of 30 Å ZnO/CdTe, collected at an incident angle of 5°. Peaks associated with polycrystalline zinc blende CdTe are marked (*). Expected peak positions for wurtzite ZnO (w-ZnO) and zinc blende ZnO (zb-ZnO) are given. Inset: High resolution XRD pattern of same film.
Relative total energies and valence-band offsets of ZnO-CdTe interfaces.
Results for bulk ZnO band gap and position of highest Zn 3d band at zone center relative to valence band maximum. Experimental band gap is for zinc blende ZnO from Ref. 14 , while Zn 3d position is estimated from wurtzite data. All results are in eV.
Valence band offsets before and after adding an extra atom to the outermost Zn or O layer of a doubled unit cell (“type (4)” to “type (5)” models) to allow formally nonmetallic solutions.
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