Raman-scattering measurements from crystalline and liquid K0.12Te0.88
and K0.50Te0.50 semiconducting alloys are reported. The spectra of liq
uid K0.12Te0.88 are characterized by a single, weakly polarized band,
markedly different from those obtained from pure liquid Te and bearing
a greater similarity to the spectra reported for amorphous Te. The sp
ectra of K0.50Te0.50 in the crystalline and liquid phases show remarka
ble similarities, confirming the presence of the Te2(2-) Zintl ion in
both phases. Substantial softening of the symmetric stretching mode oc
curs relative to the equivalent mode in vapor and matrix-isolated Te2.
This is most likely due to the charge transfer interaction with the K
+ matrix. A comparison of structural data available for liquid and amo
rphous Te with those for liquid K0.12Te0.88 and K0.50Te0.50 indicates
a transition to true 2-fold chainlike covalent bonding of Te in the li
quid on addition of potassium. The importance of 2-fold bonding for th
e semiconducting behavior of Te-rich alloy systems in the liquid and s
olid states is discussed.