Enhanced straylight suppression of short carbon nanotubes by using Platinum silicide catalyst enhancer in rapid thermal chemical vapor deposition process

Abstract

This paper focuses on the role of Platinum as a catalyst enhancer in between Inconel catalyst and silicon for the growth of vertically aligned CNT (VACNT) in a rapid thermal chemical vapor deposition (RTCVD) process for optical applications. VACNT grown over Inconel/Pt/Si showed very low hemispherical reflectance over wide ranges of wavelengths with short CNT growth of 6 um height that can significantly reduce the shadowing effects in the optical devices, an important phenomenon often compromised due to adhesive layers or from much taller CNTs. A NASA flight qualification vibration and shock tests showed CNT stability during environmental testing. The origin of such enhancements is due to the formation of nano-structured Pt-Si alloys under the catalyst layer as evident by various structural and surface characterization techniques and utilization of RTCVD. Systematic studies of CNT growth were conducted by varying the catalyst thickness, gas flow rate, temperature, and pressure during RTCVD. After optimization, we achieved hemispherical reflectance of CNT below 0.8% at 250 nm and 0.2% from 1250 to 2500 nm. Presence of vertical multi-wall CNT growth was confirmed by XPS, SEM and Raman spectroscopy. Micron-scale control over CNT heights and uniformity were achieved and confirmed by laser imaging.