Scanning Probe Microscope Investigation of Electrical Characteristics and Surface Morphology of Side Chain Liquid Crystalline Copolymers
Areefen R assamesard, T oemsak Srikhirin , T eerakiat K erdcharoen and T anak orn Osotchan** Author for corresponding; e-mail address: sctos@mahidol.ac.th
Volume: Vol.32 No.3 (SEPTEMBER 2005)
Research Article
DOI:
Received: -, Revised: -, Accepted: -, Published: -
Citation: Assamesard A..R., Srikhirin T.O.., Erdcharoen T.E..K. and Osotchan T.A.O.., Scanning Probe Microscope Investigation of Electrical Characteristics and Surface Morphology of Side Chain Liquid Crystalline Copolymers, Chiang Mai Journal of Science, 2005; 32(3): 543-548.
Abstract
The monolayer Langmuir-Blodgett (LB) films of a side chain liquid crystal copolymer (cop11) with an 11-methylene spacer and a composition of 50% nitrobiphenyl and 50% methoxy ethoxy methoxy biphenyl were prepared from the air water interface. This film was subsequently being transferred onto a hydrophobic silicon wafer substrate by horizontal deposition technique. The average thickness is 35.0 ± 1.0 Å per cop11 monolayer was investigated by X-ray reflection. The isotherms suggest molecule formation area of 23 Å2 at the air- ater interface. The monolayer of cop11 stable with surface pressure about 25 mN/m2 at the air water interface. The crack propagation of film was observed on the surface morphology of monolayer film measured by atomic force microscope (AFM) in dynamic mode. This was originated from the liquid crystal phase during transferring to the substrate. The current-voltage (I-V) characteristics of monolayer, double and three layer films were characterized by using scanning tunneling microscope (STM). The electrical current is decreased as the number of layers increasing. The tunneling current for three layer film on silicon substrate is decreased after anneal at 100 °C for 5 minutes due to molecular rearrangement.