Measurements of the Spectral and Directional Emission From Microgrooved Silicon Surfaces

This paper reports measurements of both the spectral and specular thermal radiation emission characteristics of very regularly microconfigured grooved surfaces in a silicon substrate at 300 and 400°C. The resulting surfaces were phosphorus-doped, to assure the dominance of the emission from the material near the sample surface. The samples had groove depths H of zero for a reference, to 42 μm, and widths L = 12.6 to 14 μm. The geometry repeat distance was 22 μm, or 455 grooves per cm. The grooves correspond directly in size to the band of principle emission wavelengths λ that arises at these temperature levels. The measurements show strong spectral effects for normal emission, including highly favored frequencies, for H > λ. This suggests a cavity “organ pipe” mode of emission. Similar, though modified, effects were found in directional emission, away from the normal. There also were strong polarization effects, with the cross-groove polarization mode dominant. The spectral and specular measurements are compared with calculations of the classical kind, which tacitly assume that λ < < H = 0(L).