Environmental Engineering Reference
In-Depth Information
4.3.2
Effects of Surface Modification on Defect Levels
Photoluminescence (PL) experiments have been carried out to
investigatetheeffectsofsurfacemodificationondefectlevelswithin
thebandgap.PLpeaksobservedfromTe-rich(a,b,c)andCd-rich(d,
e,f)CdTesurfacesasafunctionofphotonenergyattemperaturesof
4 K are shown in panel (a) of Fig. 4.4 [11]. Peak positions have been
converted to room temperature values using -5
×
10
−
4
eVK
−
1
for
therateofchangeoftheCdTebandgapwithtemperature[12].These
resultsindicatetheexistenceof0.72eVlevelforTe-richsurfacesand
enhancement of 0.97 eV and 1.24 eV for Cd-rich surfaces at room
temperature.PossibleelectrontransitionsduringPLmeasurements
are shown in panel (b).
Figure 4.4
(a) PL spectra observed for Te-rich (a, b, c) and Cd-rich (d,
e, f) surfaces and (b) a schematic diagram of the corresponding electron
transitions [11].
