The growth of vacuum deposited lead phthalocyanine thin films and its effects on gas sensing

The morphology and crystal structure of vapor-deposited lead phthalocyanine (PbPc) thin film depends on the substrate temperature and deposition rate. In the range of substrate temperature (25-250 degrees C) and deposition rate (0.1-5 nm/s) employed for the growth of PbPc thin films in this work, low substrate temperature and high deposition rate favor the formation of amorphous films. On the other hand, high substrate temperature and low deposition rate yield beta phase film with high crystallinity. (alpha phase film can be obtained under moderate substrate temperature and deposition rate. Film with beta structure has the slowest response in gas sensing due to its larger particle size while amorphous film with its porous structure has the fastest response in gas sensing.