Control of growth mechanism and optical properites of p-seciphenyl thin films on ionic crystal substrates

摘要

Phenylene oligomers,w hcih are low molecular weight materials of the π-conjugated polymer iof poly(p-phenylene), PPP, hve een examiend for their unique electrical and opticla properties. Recently,l the vacuum-deposited thin filsm of oligophenylenes were applied to hlight-emitting diodes (LED), non-linear optical (NLO) devices, etc. In this study, highly crystalline p-sexiphenjyl (6P) thin films were preapred on an ionic crystal subsrate (posassium chloride, KCl) by using orgaic molecualr beam deposion technique. The crystal structure, molecualr orientation and morphology of thin films prepared at different temeprautres were characterized by ransmission electronmicroscoy (TEM), aomic froce microsocpy (AFM) and X-ray difraction (XRD). It was confirmed that 6P rod-like and planar crystal having the preferential moleuclar orientations to KCl substrate surace were epitaxially grown. Thuen, preferential parallel orientatios of 6P onto KCl surface formed at lwo temperautres of 14 deg C and 50- deg C and normal ones formed at high temeprature of 150 deg C. Furtehr, it was confirmed tha the otical properties of 6P thin films were strongly infleunced by the molecualr orientaitons in crysals formed onto KC substrate surface.