Preliminary Studies in the Electrodeposition of PbSe/PbTe Superlattice Thin Films via Electrochemical Atomic Layer Deposition (ALD)

Abstract

This paper concerns the electrochemical growth of compound semiconductor thin film superlattice structures using electrochemical atomic layer deposition (ALD). Electrochemical ALD is the electrochemical analogue of atomic layer epitaxy (ALE) and ALD, methods based on nanofilm formation an atomic layer at a time, using surface-limited reactions. Underpotential deposition (UPD) is a type of electrochemical surfaced-limited reaction used in the present studies for the formation of PbSe/PbTe superlattices via electrochemical ALD. PbSe/PbTe thin-film superlattices with modulation wavelengths (periods) of 4.2 and 7.0 nm are reported here. These films were characterized using electron probe microanalysis, X- ray diffraction, atomic force microscopy (AFM), and infrared reflection absorption measurements. The 4.2 nm period superlattice was grown after deposition of 10 PbSe cycles, as a prelayer, resulting in an overall composition of PbSe0.52Te0.48. The 7.0 nm period superlattice was grown after deposition of 100 PbTe cycle prelayer, resulting for an overall composition of PbSe0.44Te0.56. The primary Bragg diffraction peak position, 2theta, for the 4.2 superlattice was consistent with the average (111) angles for PbSe and PbTe. First-order satellite peaks, as well as a second, were observed, indicating a high-quality superlattice film. For the 7.0 nm superlattice, Bragg peaks for both the (200) and (111) planes of the PbSe/PbTe superlattice were observed, with satellite peaks shifted 1 degrees closer to the (111), consistent with the larger period of the superlattice. AFM suggested conformal superlattice growth on the Au on glass substrate. Band gaps for the 4.2 and 7.0 nm period superlattices were measured as 0.48 and 0.38 eV, respectively.

Formation of PbTe nanofilms by electrochemical atomic layer deposition (ALD)

“…Electrodeposition is therefore an appealing technique for the formation of complex compound semiconductor structures, as it can be performed at or near room temperature, minimizing interdiffusion. The most notable electrodeposition techniques include precipitation [28], codeposition [29,30], two stage [31] and atomic layer deposition (ALD) [32][33][34], also known as electrochemical atomic layer epitaxy (EC-ALE).…”

Successive Ionic Layer Adsorption and Reaction (SILAR) and Related Sequential Solution‐Phase Deposition Techniques

“…160 PbSe/PbTe superlattices, with 4.2 -nm and 7.0 -nm periods, have been grown by ECALE. 161 The (111) refl ection in the XRD pattern showed a fi rst -order satellite peak and one second -order peak, indicating the formation of the superlattice. AFM images of the superlattice structure showed a small amount of three -dimensional growth.…”

“…AFM images of the superlattice structure showed a small amount of three -dimensional growth. 161 Bismuth nitrate together with sodium sulphide and tellurium oxide have been used to grow bismuth chalcogenide fi lms. 162 -166 The stoichiometric ratio 2 : 3 has been confi rmed by XPS, EDX, and XRD.…”

Electrodeposition of Semiconductors in Ionic Liquids

“…Aqueous solutions have been applied to electrodeposit binary compound semiconductors (e.g., InSb, InAs, GaAs, CdTe, CdS, etc.). Furthermore, besides classical deposition, Electrochemical Atomic Layer Epitaxy (E-ALE) and Electrochemical Atomic Layer Deposition (E-ALD) methods have been applied to deposit various semiconductors in aqueous solutions [7][8][9][10][11]. In general, the electrodeposition of semiconductors from aqueous electrolytes is strongly disturbed by hydrogen evolution that limits the electrochemical window.…”