| Photoelectron spectroscopy (PES) usually consists of X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), synchrocyclotron photoelectron spectroscopy (SRPES) and et al. It is a nondestructive surface analysis tool, and it at best can reach 10nm below the suface of a sample. Using PES, we can obtain qualitative information about the chemical state of the element and surface band distribution. We can also gain the quantitative information via PES. Combined with bombardment of Ar+, deep profile of a sample can be obtained. So PES is perfect for surface analysis and it is widely used in many domains.In this thesis, three aspects are studied based on the research project of our team using PES.1. Study of ZnO thin films grown by metal–organic chemical vapor deposition (MOCVD) via PES.We examine ZnO film prepared in some condition using PES. We examined the origin of the green luminescence peak located 450 nm-500 nm in the photoluminescent (PL) measurement. XPS results show that there are two contributions in the O 1s peak. The one around 529.9 eV is attributed to Zn-O bond in the crystall; the other locates around 531.5 eV, this position is quite different from that of Oi reported. This peak doesn't change a lot after long time bombardment of Ar+. Quantitative XPS analyses show that atom ratio of Zn:O is 2:3, indicating that oxygen is rich in this kind of ZnO film. Hall measurements show that the conductivity of the samples is unstable. So it is considered that the peak located around 531.5 eV is corresponding to a unstable state of oxygen. It will turn to be Vo or Oi. If it is Vo, the ZnO film will exhibit a n type conductivity, and Oi will lead to a p type conductivity.Arsenic-doped ZnO (ZnO:As) films are grown on GaAs layers are studied. GaAs layers are deposited on sapphire substrates by sputtering using a GaAs target, As doping is obtained by thermal diffusion. The ZnO:As films are annealed in nitrogen (ZnO:As:N2) and oxygen (ZnO:As:O2) atmosphere respectively. XPS measurements show that annealing in oxygen facilitates the form of even As doping in ZnO films and the content of As keeps around 3.4 % after Ar+ bombardment. But annealing in N2 leads to the aliquation of As at the surface for ZnO:As films. Core level results show that there are two chemical states of As in ZnO:As:O2 films including AsZn-2VZn, AsZn, while four types exist in ZnO:As:N2 films including AsZn, AsZn-2VZn, Asi and AsO. The contribution centered around 43.9 eV of As 3d peak is ascribed to AsZn-2VZn. Valence band maximum (VBM) spectrum taken by UPS indicates that the Fermi energy of ZnO:As:O2 films shifts toward the VBM by 0.37 eV compared with undoped ZnO films, which proves AsZn-2VZn is a acceptor in ZnO:As:O2 films. But the ZnO:As films still show n type conductivity, which is possibly due to the compensation of As-related donor and native defects.Detail analysis of chemical states of As in ZnO may help point toward paths to grow high quality ZnO:As films.2. Study of ErF3 doped near infrared (NIR) luminescent material via PES.We demonstrated near-infrared (NIR) organic light-emitting devices (OLEDs) employing erbium fluoride (ErF3) doped into tris-(8-hydroxyquinoline) aluminum (Alq3). The device structure was ITO/ N, N′-di-1-naphthyl-N, N′-diphenylbenzidine (NPB)/ Alq3: ErF3/ 2,2 ',2 ''-(1,3,5-phenylene) tris (1-phenyl-1H-benzimidazole) (TPBI)/ Alq3 /Al. ErF3 was synthesized by mixing hydrofluoric (HF) acids and erbium oxide (Er2O3) in a Teflon-lined autoclave. Room-temperature electroluminescence was observed around 1530 nm due to 4I13/2 -4I15/2 transition of the Er3+. The full width at half maximum (FWHM) of the electroluminescent (EL) spectra was ~ 50 nm. The NIR EL intensity from the ErF3-based device was ~ 4 times higher than that of Er(DBM)3Phen-based device at the same current.The doping mechanism of ErF3 in Alq3 is investigated by PES, LiF doped Alq3 is also studied for comparison. It is found that there is a charge transfer between host and dopant in the Alq3–LiF systems, and F- anion acts as an n-type donor. For ErF3, XPS results show that Er atoms will partly replace Al atoms in ErF3 doped Alq3, and Er atoms obtain electron charge from Alq3. UPS results show that the influence of ErF3 doping to work function of Alq3 is opposite to that of LiF.The mechanism of electroluminescent is attributed to F?rster energy transfer mechanism to NIR-OLED.3. By adding a micro-gas-in gun to PES system, we carry out in situ PES to study the SnO2-based CO gas sensor.Considering the work condition of gas sensor, we modified our PES system by adding a micro-gas-in gun. Then we can carry out in situ PES to study the interaction between SnO2 and CO gas at a high temperature.We parpare SnO2 powders by sol-gel, Pd,Th doping are obtained by adding PdCl2, and ThO2 to SnO2 powders and sintered in muffle furnace. XRD results show that the sample has the sample stucture as rutile. SEM results show that the grain size decreases after doping. Quantitative XPS analyses show that atom ratio of Sn:O isn't 1:2, and Sn is rich. O 1s spectrum got by XPS exhibits two contributions, the one around 529.8 eV is attributed to Sn-O bond (Olat); the other locates around 532.0 eV is attributed to adsorbed oxygen(Oads) due to the defects of surface.We examine the interaction between SnO2 and CO gas at 150℃in situ. No change is found for Sn 3d and C 1s core level. Quantitative XPS analyses show: (1) atom ratio of Sn: Olat changes from 1:1.05 without CO to 1:1.08 with CO flowing through the sample surface; (2) without gas the atom ratio of Sn: Oads is 1:0.56, with CO the ratio is 1:0.33. This means CO react with SnO2, Oads plays an important role. VBM spectrum taken by UPS indicates that the VBM of SnO2 shifts toward the Fermi energy by 0.1 eV with CO. It indicates that electrons transfer to SnO2 in this reaction, this transfering leads to band bending of the surface. So it can be presumed that such a reaction has happened as below: We also examine the additives in SnO2. There is no obvious change for the binding energy of Th 4f and Pd 4d. We think it needs furthure research to clarify the sensitization mechanism of the additives.
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