On-line diagnostics for Langmuir-Blodgett film growth☆

Abstract Prototype capacitance sensors, composed of interdigitated contacts, have been fabricated and evaluated. Measurements during deposition in a Langmuir-Blodgett trough and measurements subsequent to multilayer deposition confirm that the technique is capable of monitoring film growth in real-time. Changes of 0.01 pF per monolayer of poly(methyl methacrylate) deposited onto glass were measured against a background of 58 pF. Identical results were obtained using both a capacitance meter and a spectrum analyzer. It appears that a factor of 10 in sensitivity can be readily obtained by reduction of the width of the sensor lines from 50 to 5 μm. This will permit the use of several sensors to monitor differential effects of deposition over the substrate. In particular, this technique is expected to permit accurate evaluation of the behavior of water during deposition and drying.