Abstract
We report on the fabrication of shellac thin films on silicon substrates by matrix-assisted pulsed laser evaporation (MAPLE) using methanol as matrix. Very adherent, dense, and smooth films were obtained by MAPLE with optimized deposition parameters, such as laser wavelength and laser fluence. Films with a root mean square (RMS) roughness of 11 nm measured on 40 × 40 µm2 were obtained for a 2000-nm-thick shellac film deposited with 0.6 J/cm2 fluence at a laser wavelength of 266 nm. The MAPLE films were tested in simulated gastric fluid in order to assess their capabilities as an enteric coating. The chemical, morphological, and optical properties of shellac samples were investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and atomic force microscopy (AFM).
Highlights
Shellac is a biomaterial, a resin secreted by the female lac bug Kerria lacca on the trees in India and Thailand
The deposition of shellac thin films by matrix-assisted pulsed laser evaporation (MAPLE) has proven to be successful by utilization of a UV laser
We have obtained films with a thickness of 2000 nm and an root mean square (RMS) roughness less than 1% of the thickness for the optimal set with a thickness of 2000 nm and an RMS roughness less than 1% of the thickness for the optimal set of deposition parameters
Summary
A resin secreted by the female lac bug Kerria lacca on the trees in India and Thailand. It consists of esters and polyesters of polyhydroxy acids. Shellac can be deposited by drop casting from a solution with ethanol or methanol. Shellac thin films have a dielectric constant between 3 and 5 [3] and very low surface roughness. They have been used as a substrate for organic field-effect transistor (OFET) and as a gate dielectric [3]. The solution has to evaporate for about half an hour at 50 ◦ C and it has to be heated for an hour at 70 ◦ C in order to obtain roughness lower than 1 nm [3]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
