Stainless steels are used in an array of applications where their ability to take on colour is of aesthetic value. Although thermal colouring (heat tinting) is known, particularly in terms of its effect on welds, the surface development of thermally coloured stainless steel has not been considered in detail. This paper demonstrates the colour development of a bright annealed 304 stainless steel with time at temperature. The colour development has been quantified using colour spectrophotoscopy and the colour related to the growth of surface oxide features by Scanning Electron Microscopy and the chemical profiles by X-ray Photoelectron Spectroscopy (XPS). There is a clear development of both the oxide thickness and chemistry, with increasing time with small nodules being the main features seen across the surface of the samples with time. The oxides have been shown to comprise of an outer iron rich oxide and an inner chromium/iron spinel layer.

A 6-period GaAs/Al0.9Ga0.1As distributed Bragg reflector (DBR) has been grown and its optical properties have been both measured and simulated. Incremental improvements were made to the simulation, allowing it to account for internal consistency error, incorrect layer thicknesses, and absorption due to substrate doping to improve simulation accuracy. A compositional depth profile using secondary-ion mass spectrometry (SIMS) has been taken and shows that the Al fraction averages 88.0% ± 0.3%. It is found that the amplitude of the transmission is significantly affected by absorption in the n-doped GaAs substrate, even though the energy of the transmitted light is well below the GaAs band gap. The wavelength of the features in the transmission spectrum are mostly affected by DBR layer thicknesses. On the other hand, the transmission spectrum is found to be relatively tolerant to changes to Al fraction.