Native defect changes in cds single crystal platelets induced by vacuum heat treatments at temperatures up to 600°C

Effect of cooling rate of pre-annealed CdS thin film electrodes prepared by chemical bath deposition: Enhancement of photoelectrochemical characteristics

“…Thus slowly cooled CdS film electrodes have better crystallite uniformity and better matrix inter-grain cross-linkage. Parallel to mono-crystalline electrodes [31][32][33][34][35][36][37], PEC characteristics for the slowly cooled film electrodes are expected to be better than those for quenched counterparts.…”

Dynamics of Bound Exciton Complexes in CdS Nanobelts

“…One of the important findings by Christmann et al using a mass spectrometer was that the rate of loss of Cd compared to S is much smaller when CdS platelets were heated and the sulfur vacancies dominate the surface depletion layer. 28 They also found that sulfur leaves the single-crystal CdS at temperature as low as 100°C, creating a depletion layer mainly formed by sulfur vacancies. Sulfur vacancy is also a major source of surface defects in CdS nanocrystals.…”

Giant Quantum Yield Enhancement in CdS/MgF2/Ag Hybrid Nanobelt under Two-Photon Excitation

“…Over the past two decades, quasi one-dimensional (1-D) semiconductor nanostructures, such as nanowires and nanobelts, have been intensively studied. − These nanostructures demonstrate excellent optical and electric properties compared with those bulk counterparts. − However, due to large surface-to-volume ratios of nanostructures, surface defects, such as element vacancies and interstitials in the surface, are the dominant defect states in the nanostructure with good crystallinity. For example, since the loss rate of sulfur (S) in traditional CdS structures is much larger than that of cadmium (Cd; S is easily escaped at the temperature as low as 100 °C), a surface depletion layer can be easily created on the surface of the nanostructure due to S vacancies. , As a result, it induces a localized trap level in the band gap and captures the electrons, leading to fluorescence quenching due to nonradiative electron–hole recombination. Specifically, free carriers can be significantly trapped by S vacancies due to a long diffusion length (∼650 nm at room temperature) in CdS NWs, resulting in a fast nonradiative recombination channel (even several times faster than radiative recombination). , Thus, surface defects significantly degrade the optoelectronic performance of nanostructures.…”

“…According to Table , the defect density in the CdS/MgF 2 /Ag hybrid is decreased from (3.7 ± 1.9) × 10 19 cm –3 to (3.9 ± 0.6) × 10 18 cm –3 in comparison with the bare CdS nanobelt, indicating that the surface defects of the CdS nanobelt are passivated effectively. In CdS, the S element more easily escaped due to a lower boiling point than that of Cd, , forming a deep level (1.8 eV) of the traps on the surface, and it is well-known that the fluorine (F) element can fill the S vacancy on the surface and repair the energy band, so that coating MgF 2 is an important method to passivate the CdS nanobelt. , Furthermore, in order to directly validate the passivation of MgF 2 , TRPL of CdS nanobelt covered by 10 nm MgF 2 is measured. The results demonstrate that the defect density in CdS/MgF 2 is reduced to 3.5 × 10 18 cm –3 , which is similar to that in the CdS/MgF 2 /Ag hybrid (see SI for more details).…”

“…For example, since the loss rate of sulfur (S) in traditional CdS structures is much larger than that of cadmium (Cd; S is easily escaped at the temperature as low as 100 °C), 7 a surface depletion layer can be easily created on the surface of the nanostructure due to S vacancies. 12,13 As a result, it induces a localized trap level in the band gap and captures the electrons, leading to fluorescence quenching due to nonradiative electron−hole recombination. Specifically, free carriers can be significantly trapped by S vacancies due to a long diffusion length (∼650 nm at room temperature) in CdS NWs, resulting in a fast nonradiative recombination channel (even several times faster than radiative recombination).…”