Thin films of narrow−gap (∠0.6 eV) semiconductors should be good selective solar absorbers since they absorb in the solar spectrum (<2 μ) but transmit in the infrared (≳2 μ). Unfortunately, semiconductors have high indices of refraction which give high reflectivity from smooth surfaces and thus have poor solar−absorbing efficiency. In this investigation, the effect of deposition conditions on surface morphology and solar absorptivity of silicon, germanium, and lead sulfide thin films is examined. It is found that the solar absorptivity of germanium films can be greatly increased by ’’gas evaporating’’ them in a low−pressure (20 mTorr) argon atmosphere apparently due to changes in the film−surface morphology. Solar absorptances of greater than 95% are obtained from 1−μ thick films of gas−evaporated germanium and vacuum−evaporated PbS films. Gas−evaporated silicon films showed a shift in the absorption edge which makes them unacceptable for solar absorbers.