Phase Control of Manganese Dioxide Thin Films by Plasma Assisted Laser Ablation PDF Download

Author: Maya Nadim Abi Akl
Publisher:
ISBN:
Category :
Languages : en
Pages : 192

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Book Description
The aim of this work is to investigate the growth of manganese dioxide thin film s by conventional Pulsed Laser Deposition (PLD) and Remote Plasma Assisted-PLD (RPA-PLD) in order to assess the role of plasma activation on promoting high oxid ation state of manganese and to improve the structural and morphological properties of the grown layers. For this purpose, films were grown on Si (100) substrate by K rF excimer laser ablation of a MnO target. The effects of substrate temperature, oxygen pressure and plasma activation on composition, crystallinity, structure, surface morphology, and growth rate were studied using Grazing Incidence X-Ray Diffraction (GIXRD), Fourier Transform Infra-Red Spectroscopy (FTIR), Raman Spec troscopy, Atomic Force Microscopy (AFM) and Surface Profilometry. The optimal temperature to grow manganese dioxide films in terms of crystalline quality was found to be 500 degreesC. Crystallinity appears to deteriorate at lo wer deposition temperature, while at higher temperature, the Dimanganese trioxid e phase is stabilized. Deposition at high oxygen pressures (250 and 500 mTorr) r esulted in the formation of stoichiometric manganese dioxide films, but the unde rlying structure of the layers was identified as gamma-manganese dioxide, consis ting of an irregular intergrowth of R- and beta-manganese dioxide which caused b roadening of XRD peaks and IR bands. Plasma activation of the process leads to l ittle improvement of film quality in this range of pressure. Alternatively, oper ation at low pressure values (1 to 50 mTorr) with plasma assistance was examined . While deposition in oxygen ambient in this pressure range led to the formation of di-manganese trioxide and Hausmanite, plasma activation induced a shift in t he Mn-O phase diagram allowing the synthesis of manganese dioxide, even at such low pressures. The corresponding films consisted of pure and highly crystalline beta-manganese dioxide with extremely smooth sur faces of roughness values as low as 0.5 nm. Such results highlight the necessity of using RPAPLD when aiming to grow high quality oxide films such as manganese dioxide.