Effect of 120 MeV Au9+ ion irradiation on the structure and surface morphology of ZnO/NiO heterojunction

• Published in: Surface and interface analysis Vol. 50; no. 10; pp. 954 - 961
• Main Authors: Das, Pankaj Kumar, Biswal, Rajib, Choudhary, Ram Janay, Sathe, Vasant, Ganesan, Vedachalaiyer, Khan, Saif Ahmad, Mishra, Naresh Chandra, Mallick, Pravanjan
• Format: Journal Article
• Language: English
• Published: Bognor Regis Wiley Subscription Services, Inc 01.10.2018
• Subjects: Atomic beam spectroscopy; atomic force microscope; Atomic force microscopy; Buffer layers; Compressive properties; Fluence; Heterojunctions; heterostructure; Ion irradiation; Morphology; Nickel oxides; Photovoltaic cells; Pulsed laser deposition; Pulsed lasers; Raman spectra; Recrystallization; Roughness; Silicon substrates; Spectrum analysis; stress; Stresses; Stretching; Surface layers; Thickness; Thin films; X-ray diffraction; Zinc oxide
• ISSN: 0142-2421; 1096-9918
• DOI: 10.1002/sia.6512

ZnO/NiO thin films, each of thickness 100 nm, were deposited on Si(100) substrate by pulsed laser deposition method. The resulting heterojunction, ZnO/NiO/Si, was irradiated by 120 MeV Au9+ ions and characterized by grazing incidence X‐ray diffraction (GIXRD), Raman spectroscopy, and atomic force microscopy (AFM). The GIXRD confirmed the presence of both NiO and ZnO in the samples. Ion irradiation induced suppression of crystalline nature, and the recrystallization of the same occurred at the fluence of 1 × 1013 ions cm−2. The occurrence of most intense band at 302 cm−1 in Raman spectra corresponds to the symmetric stretching vibration of ZnO. The linear shift of stretching mode of ZnO with ion fluence could be associated with the effect of compressive stress in the material. AFM analysis of the films indicated that the rms roughness increased when the film is irradiated at a fluence of 1 × 1012 ions cm−2. Beyond this fluence, the value of roughness decreased up to fluence of 1 × 1013 ions cm−2 and increased thereafter. To see the effect of the stress of buffer layer on the surface layer, we calculated the stress for NiO layer with ion fluence form the lattice parameter. Comparing the stress of buffer layer with roughness of surface layer at the given fluence, we can say that the compressive stress in the buffer layer could possibly control the roughness of the surface layer.