Properties of Films Based on Nanosize and Submicrometer InSb Particles Passivated with CdS
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ties of Films Based on Nanosize and Submicrometer InSb Particles Passivated with CdS M. I. Shishkina*, Yu. V. Nikulina, and E. S. Prikhozhdenkoa a
Saratov State University, Saratov, 410012 Russia *e-mail: [email protected]
Received February 20, 2020; revised July 10, 2020; accepted July 15, 2020
Abstract—An increase in the reflection in the IR spectral range typical of a plasmon resonance in single crystals is observed in an InSb film formed by thermal evaporation in a vacuum on a CdS single crystal. Raman spectra demonstrate an approximately constant ratio between the amorphous and crystalline phases for InSb films on a CdS substrate, which is uncharacteristic of an InSb film on gallium–gadolinium garnet. The current–voltage characteristics of an InSb film on CdS are linear, as also those of an annealed sheet of InSb (core)–CdS (shell) quantum dots and, in addition, become sensitive to illumination. Keywords: semiconductor films, colloidal quantum dots, passivation, Raman spectroscopy. DOI: 10.1134/S1063785020100296
Because of the large values of the de Broglie wavelength (~100 nm), quantum-confinement effects appear in the InSb semiconductor in crystallites and films with thicknesses of up to 100–200 nm. There is particular interest in structures of this kind as concerns measurements of electrical and optical properties associated with the behavior of free carriers under quantum-confinement conditions. As particles become smaller, the role played by the surface sharply grows, which leads to capture of carriers by surface states. The passivation of III–V materials and, in particular, InSb with silicon oxides [1], sulfides [2], and nitrogen [3] can diminish surface leakage currents [4] and lead to disappearance of hysteresis in capacitance–voltage characteristics [1, 4], enhance photoluminescence [3, 5], and make current–voltage I(U) characteristics linear [6]. It should be noted that, nearly always, what is in question is the surface passivation of single crystals, which makes it possible, for example, to suggest that the annealing at a temperature close to the InSb degradation temperature affects the passivation [2], but gives no information about the surface itself, which may be a thin-film layered-barrier structure. Its properties frequently depend on the way in which these layers are obtained (bottom up and top down), similarly to studies of CdTe [7], which made it possible to diminish the surface recombination and obtain samples that are highly sensitive to light. Therefore, it is reasonable to examine electronic processes in similar structures constituted by quantum-confined InSb particles. An analysis of these processes from the
standpoint of passivation that was the goal of our study. As objects of study served polycrystalline InSb films and also sheets of quantum dots (QDs) of the material, deposited from a colloidal solution. It is known that the sulfide passivation of InSb QDs favorably affects their optical properties, e.g., their photoluminescence [8]. This fact, as well as the growing int
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