Excimer pulsed laser deposition of diamond-like carbon films

Abstract

Hydrogen-free Diamond-like Carbon(DLC) films onto silicon wafer are deposited by pulsed laser deposition(PLD) at a substrate temperature of 25 °C in vacuum. The laser source used was an 20 ns KrF excimer laser beam with the wavelength of 248 nm and maximum laser energy of 600 mJ at a repetition rate of 10Hz. The laser intensity used vary from 1.02×109W/cm² to 2.24×109W/cm². Infrared transittance, Raman spectroscopy and nano-hardness are used to analyze the comprehensive performance of the films, and the results show that the film deposited at laser intensity of 1.28×109W/cm² is the best among other films. This can be explained well by that the carbon ion energy at laser intensity of 1.28×109W/cm² is suitable to form sp³ bonds than sp² bonds. If carbon ion energy is too low, it has not enough energy to from sp³ bonds. While, if carbon ion energy is too high, extra energy will transfer sp³ bonds to sp² bonds. Raman spectrum measurement showed a unsymmetrical broad peak with a center at 1550 cm^-1 for all films. The ID/IG calculated by Gaussian fit of Raman spectrum is as low as 0.44. There are few graphite particles on these DLC films. The nano-hardness of DLC films is relatively high. The DLC films improve Silicon wafers' anti-scratch performance efficiently. The DLC films are scratched 100000 times under 9.8N press on RS-5600 films scratch machine, no nick is observed after scratch. The highest IR transmittance between 3 and 5μm of Silicon wafers increase 22%, from 54.5% to 66.5% after coated by DLC films, which approaches the highest IR transmittance in theory. The mean IR transmittance between 3 and 5μm of the Diamond-like Carbon films deposited at laser intensity of 1.28×109W/cm² is 65.6%.