Thermal oxide on CdSe

Abstract

Articles you may be interested inInvestigation of the surface chemical and electronic states of pyridine-capped CdSe nanocrystal films after plasma treatments using H 2 , O 2 , and Ar gases Effects of surface passivation on the exciton dynamics of CdSe nanocrystals as observed by ultrafast fluorescence upconversion spectroscopy X-ray photoelectron spectroscopy ͑XPS͒ has been used to characterize the thin thermal oxide film grown on single crystal CdSe͑0001͒ and polycrystalline CdSe by exposure to O 2 ͑dry air͒ at 350°C. SeO x species, where xϭ2,3, are clearly identified by a 5 eV shift of the Se 3d 3/2,5/2 peaks to higher binding energy. A very weak shift to lower binding energy is observed for the Cd peaks. The positions of the Cd and O peaks do not match those found for the known cadmium oxides, CdO and CdO 2 . Instead, it is proposed that the Cd bound oxygen atoms occupy substitutional Se sites. The presence of Cd bound oxygen can also be inferred from the intensities of the SeO x , Cd, and O peaks. Raman spectroscopy confirms the existence of O in Se substitutional sites. Angle-resolved XPS is used to determine the thickness of the oxide and the relative amount of SeO x and Cd bound oxygen. The XPS data are consistent with an 8-9 Å thick oxide where ϳ60% of the oxygen is bound to Se and ϳ40 is bound to Cd. The data show that the oxide structure contains two layers; a passivation layer made of the SeO x species and, underneath, a layer containing oxygen in Se substitutional sites.

One-step electrodeposition of CdSe on nanoparticulate titania films and their use as sensitized photoanodes for photoelectrochemical hydrogen production

“…at approximately 145 cm −1 and 635 cm −1 , are assigned to the TiO 2 (anatase) substrate. According to the literature [14] a weak Raman band appears at ∼440 cm −1 in the oxidized CdSe samples; similar band was not observed in our spectra (inset in Fig. 4) verifying the fact that the only detectable species is CdSe.…”

Structural evolution and optical properties of CdSe nanocrystals prepared by mechanical alloying

“…The chemical shift by 4.3 eV for the peak of Se 3d core level was attributed to oxidation of Se on the surface of CdSe nanoparticles. The magnitude of Se 3d chemical shit for selenium oxide is dependent on the number of neighboring oxygen atoms [49,50]. A shift of 3 eV with respective to bulk Se 3d 5/2,3/2 is corresponding to SeO, a shift of around 4.5 eV to SeO 2 and SeO 3 , as well as 6.0 ± 0.5 eV to SeO 4 .…”

Thiocyanate functionalized ionic liquid electrolyte for photoelectrochemical study of cadmium selenide pebbles

“…peak a 2 and peak b 2 observed beneath the peak a 1 and peak b 1 , and showed very weak shifting in peak positions. Thermal oxidation of CdSe has been already reported with a very weak shift of Cd(3d 5/2 ) and Cd(3d 3/2 ) core levels [32,33]. The weak shifting of Cd(3d 5/2 ) and Cd(3d 3/2 ) core levels in our annealed samples is indicative of CdO formation [34].…”

“…6.77 eV) between these two peaks also indicates the probable formation of CdO [30]. However, the less intensity of the peaks a 2 and b 2 than that of a 1 [31,33]. The values of binding energy of Cd3d 5/2 , Cd3d 3/2 and Se3d 5/2 , Se3d 3/2 are summarized in Table 1.…”