Optical and photoemission studies of TmTe

We report here on the optical absorption of TmTe films (5<T<300 K; 0.2<h<4.5 eV) and the reflectance (0.2<h<20 eV) and ultraviolet photoemission spectra (UPS; 15h90 eV) of vacuum- and air-cleaved TmTe single crystals. Much of the structure seen in absorption and reflectance spectra can be attributed to transitions from Tm2+, e.g., the first absorption band centered at 0.7 eV is identified as due to a transition from Tm2+ 4f134f12(H63)5d(t2g). No optical structure was seen which would permit us to identify Tm3+ in TmTe. The UPS data show a small amount of Tm3+ which was, however, strongly influenced by surface conditions in spite of in situ study in a vacuum of 10-10 Torr. We conclude that Tm is essentially divalent in TmTe. © 1975 The American Physical Society.