非掺杂ZnO薄膜中紫外与绿色发光中心

用直流反应溅射方法在硅衬底上淀积了ZnO薄膜,测量它们的光致发光(PL)光谱,观察到两个发光峰,峰值能量分别为3.18(紫外峰,UV)和2.38eV(绿峰).样品用不同温度分别在氧气、氮气和空气中热处理后,测量了PL光谱中绿峰和紫外峰强度随热处理温度和气氛的变化,同时比较了用FP-LMT方法计算的ZnO中几种本征缺陷的能级位置.根据实验和能级计算的结果,推测出ZnO薄膜中的紫外峰与ZnO带边激子跃迁有关,而绿色发光主要来源于导带底到氧错位缺陷(O_Zn)能级的跃迁,而不是通常认为的氧空关键词：ZnO薄膜热处理光致发光光谱缺陷能级

THE ULTRAVIOLET AND GREEN LUMINESCENCE CENTERS IN UNDOPED ZINC OXIDE FILMS

Undoped ZnO films were deposited on Si substrates by DC reactive sputtering. The samples were annealed in air, pure O₂ (1atm) and pure N₂ (1atm) at 850℃,950℃,1000℃ for 1h. The X-ray diffraction patterns of the as-deposited and annealed samples all have a widened diffraction peak of ZnO (002). It is evident that all the films we used are ZnO films with [001] orientation. The photoluminescence (PL) spectra of these samples include two emission peaks, centered at 3.18eV (ultraviolet, UV) and 2.38eV (green). It is fount that the intensities of these peaks vary with annealing temperature and atmosphere. At same annealing temperature, the intensity of green peak increases evidently with the increase of oxygen partial pressure, and the intensity of UV peak is also increased somewhat. In the same atmosphere, the intensity of green peak enhances sharply with the increase of annealing temperature, but the intensity of UV peak increases slowly and approaches a maximum value at 950℃, then decreases as the annealing temperature increases.; We investigated the dependence of the crystallization and also the intrinsic defects in ZnO film, such as zinc vacancy V_Zn, oxygen vacancy V_O, interstitial zinc Zn_i, interstitial oxygen O_i and anti-sited oxygen O_Zn on the annealing conditions. Compared with the calculated data of these intrinsic defects, it is suggested that the UV radiation of ZnO is due to band-edge exciton transition, and the green emission corresponds to the transition from the bottom of the conduction band to the local level composed of oxide misplaced defects.