CdSe single crystals with n- and p-type of conductivity approaching intrinsic

Baubinas, R.; Januškevičius, Z.; Sakalas, A.

doi:10.1016/0025-5408(73)90189-x

Cited by 8 publications

(5 citation statements)

References 12 publications

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“…Close agreement between the E VBM shift (Δ E VBM = 0.45 ± 0.05 eV) and the aforementioned E VAC and Cd 4d 5/2 BE shifts in the XPS data, after sputtering the AE Xtal surface, lends credence to this approach for determination of VBM and indicates an upward shift in the band edges wrt E F (i.e., band bending) , within the near-surface region of the Spt Xtal surface. This band bending is consistent with the formation of a depletion layer after sputtering and is attributed to near-surface Se-enrichment (Figure C), which fills Se vacancies responsible for the n-type conductivity of CdSe Xtals . We suggest that a smaller shift for the Cd 3d 5/2 CL BE (0.15 ± 0.04 eV), in Figure B, after sputtering the AE Xtal surface indicates that the XPS probe depth (ca.…”

Section: Resultssupporting

confidence: 75%

“…Using these modified approaches for quantification of relative atomic ratios from these XPS data, we find a Se/Cd atomic ratio of 0.94 for the sputtered CdSe(0001) surface, suggesting only a slight enrichment of surface Cd relative to surface Se after the acid-etch/sputtering process to expose the cleanest possible surface. Such a Cd-rich surface region is consistent with n-type conductivity originating from near-surface Se vacancies . The AE Xtal surfaces are slightly more Cd-rich (Se/Cd = ca.…”

Section: Resultssupporting

confidence: 67%

“…This band bending is consistent with the formation of a depletion layer after sputtering and is attributed to near-surface Se-enrichment (Figure 3C), 83 which fills Se vacancies responsible for the n-type conductivity of CdSe Xtals. 82 We suggest that a smaller shift for the Cd 3d 5/2 CL BE (0.15 ± 0.04 eV), in Figure 3B, after sputtering the AE Xtal surface indicates that the XPS probe depth (ca. 9−10 nm) is similar to the depletion layer width, which is expected of heavily doped (ρ < 1 Ω cm) n-type CdSe Xtal.…”

Section: ■ Results and Discussionmentioning

confidence: 80%

“…Such a Cd-rich surface region is consistent with n-type conductivity originating from near-surface Se vacancies. 82 The AE Xtal surfaces are slightly more Cd-rich (Se/Cd = ca. 0.88), with a small O LBE /Cd ratio, and the AE Xtal surfaces which were air-plasma etched (AP) are even more Cd-rich (Se/Cd = ca.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Influence of the Processing Environment on the Surface Composition and Electronic Structure of Size-Quantized CdSe Quantum Dots

et al. 2020

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We show here how differences in surface composition for monolayer (ML)-tethered pyridine (Py)-treated CdSe quantum dots (QDs) affect band edge energetics, as a function of QD diameter. We compare UV−vis spectroscopy of QD solutions and X-ray (XPS) and ultraviolet (UPS) photoelectron spectroscopy of QDs tethered to 1,6hexanedithiol-modified Au surfaces. Differences in QD surface composition are brought about by differences in solvent composition during displacement of the native, X-type octadecylphosphonate (ODP − ) ligands with Py and by differences in exposure to trace H 2 O and O 2 during QD processing. Prior to surface tethering, exchange of the ODP − ligands with Py ligands under ambient (A) conditions leads to some surface passivation of the QD and no appreciable reduction in the spectroscopically estimated QD diameter. QDs processed in completely inert (I) environments (O 2 and H 2 O below detection limits in the solvents, processing environments, and during analysis) undergo a small decrease in diameter during Py exchange and an increase in size dispersity. These simple differences in processing conditions lead to important differences in QD band edge energetics which will impact their use as photocatalysts and photovoltaic or light-emitting diode active layers. XPS characterization of Py-capped QD-tethered MLs, compared with freshly etched CdSe(0001) single-crystal surfaces, indicates that I QDs show a higher Se surface coverage relative to A QDs. For A QDs, we propose that trace H 2 O present during processing provides a proton source that facilitates ODP − desorption and replacement with charge-compensating HO − ligands, which inhibits subsequent changes in QD surface composition. UPS-derived size-quantized ionization potentials (IPs) and electron affinities (EAs) for I QDs, corrected for shifts in the local vacuum level, closely track the energetic shifts predicted by the effective mass approximation (EMA). The vacuum level-corrected IP/EA values for A QDs show sizeable deviations from the EMA. We also describe an approach for characterization of UPS data for these QD MLs, which greatly enhances the sensitivity to mid-gap states above the VBM (seen for I QDs which are slightly enriched in surface Se) and offers a general approach to all semiconductor materials with low density of states in the valence band region. This study confirms the influence of ligand modification and processing environment on QD surface composition, which in turn impacts the CdSe QD energy levels that are important to applications in photocatalysis and optoelectronic device platforms.

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Section: Resultssupporting

confidence: 75%

Section: Resultssupporting

confidence: 67%

Section: ■ Results and Discussionmentioning

confidence: 80%

Section: ■ Results and Discussionmentioning

confidence: 99%

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Influence of the Processing Environment on the Surface Composition and Electronic Structure of Size-Quantized CdSe Quantum Dots

et al. 2020

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“…The achievement of p-type CdSe is still challenging so far due to the self-compensation effect in the material. Ohtsuka et al reported that p-type CdSe could be achieved by molecular beam epitaxy using a nitrogen plasma source [59,60]. However, there is generally a lack of facile methods for producing p-type CdSe.…”

Section: Cdsementioning

confidence: 99%

Electrodeposition Fabrication of Chalcogenide Thin Films for Photovoltaic Applications

et al. 2020

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Electrodeposition, which features low cost, easy scale-up, good control in the composition and great flexible substrate compatibility, is a favorable technique for producing thin films. This paper reviews the use of the electrodeposition technique for the fabrication of several representative chalcogenides that have been widely used in photovoltaic devices. The review focuses on narrating the mechanisms for the formation of films and the key factors that affect the morphology, composition, crystal structure and electric and photovoltaic properties of the films. The review ends with a remark section addressing some of the key issues in the electrodeposition method towards creating high quality chalcogenide films.

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Analysis of the preparation conditions of undoped p-CdSe, p-CdS, p-ZnSe, and n-ZnTe single crystals

Sakalas

1975

Phys. Stat. Sol. (a)

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By a simple analysis the quenching temperatures and partial pressures of components were found at which undoped p‐CdSe, p‐CdS, p‐ZnSe might be obtained. It follows, that p‐CdSe and p‐CdS may be produced by heating the crystals under excess chalcogen pressures at temperatures not exceeding 1140 °K for CdSe and 1040 °K for CdS. p‐ZnSe may be obtained in a wide range of temperatures and pressures. Experimental results are in agreement with the given analysis. As follows from the analysis, ZnTe is likely to exist only of p‐type.

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CdSe single crystals with n- and p-type of conductivity approaching intrinsic

Cited by 8 publications

References 12 publications

Influence of the Processing Environment on the Surface Composition and Electronic Structure of Size-Quantized CdSe Quantum Dots

Influence of the Processing Environment on the Surface Composition and Electronic Structure of Size-Quantized CdSe Quantum Dots

Electrodeposition Fabrication of Chalcogenide Thin Films for Photovoltaic Applications

Analysis of the preparation conditions of undoped p-CdSe, p-CdS, p-ZnSe, and n-ZnTe single crystals

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