Fabrication Of The Functional Semiconductor Nanofilms By Electrochemical Atomic Layer Deposition(EC-ALD) And Their Application

In this thesis, the electrochemical atomic layer deposition (EC-ALD) method was used to fabricate several functional semiconductor compounds on different substrates, and the application of these thin films such as photoelectrocatalysis and organic degradation were also investigated. Electrochemical aspects were characterized by means of cyclic voltammeter (CV), Amperometric I～t, open circuit potential (OCP), and differential pulse voltammeter (DPV). The structures, morphologies, composition and functional behaviors of the deposited thin films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electronic microscopy (FE-SEM) with an energy dispersive X-ray (EDX) analyzer, and FTIR studies. The main issues of this thesis were described as follows:1. Study of ZnSe deposition on Au Substrate by EC-ALDStudies of the electrochemical optimization of ZnSe thin film deposition on polycrystalline Au substrates using EC-ALD are reported. Electrochemical aspects were characterized by means of cyclic voltammetry, differential pulse voltammetry, and coulometry. To study the growth mechanism of the underpotential deposition in the formation of ZnSe, the effects of Zn and Se deposition potentials and a Se-stripping potential were adjusted to optimize the deposition program. The deposit, grown using the optimized program, was proved to be a single-phase ZnSe compound with a strong (220)-preferred orientation by XRD analysis, and SEM observation shows the deposit consisted of nanoscale particles with an average size about 100 nm. The right 1:1 stoichiometric ratio of Zn to Se according to the coulometry suggests that ZnSe is formed.2. Study of Cu2Se deposition on Au Substrate by EC-ALDOptimization of Cu2Se thin films deposition on Au substrates using EC-ALD is reported here. Single atomic layers were formed using surface limited reactions, referred to as underpotential deposition (UPD). A steady EC-ALD deposition for Cu2Se compound could be attained after appropriate adjusting the UPD potentials of Cu and Se on Au in steps over the initial 20 cycles, and the potentials could be kept constant for the following deposition. A 200-cycle deposit, which was grown with the steady deposition potentials of Se at-0.35V and Cu at 0.10V, was proved to be a single phase Cu2Se compound by XRD analysis, with a preferential (111) orientation without annealing. Electron probe microanalysis (EPMA) indicated a uniform and stoichiometric deposit, with a Cu/Se ratio of 2.3. Study of CuTe and Cu2Te deposition on ITO Substrate by EC-ALDAn EC-ALD method for fabrication of CuTe and Cu2Te thin films is presented. The films'growth is based on the epitaxial electrodeposition of Cu and Te alternately with different electrochemical parameter respectively. The deposited thin films were characterized by XRD, field emission scanning electronic microscopy (FE-SEM) with an EDX analyzer, and FTIR studies. The results suggest that EC-ALD is an ideal method for deposition of compound semiconductor films for photoelectric applications.4. Study of Cu2ZnSnS4 (CZTS) deposition on Ag Substrate by EC-ALDQuaternary compound semiconductor Cu2ZnSnS4 (CZTS), which appears to be a promising candidate for the absorber of a thin film type solar cell, was grown on polycrystalline Ag substrates by electrochemical epitaxial method. The deposited thin films were characterized by XRD, FE-SEM with an EDX analyzer, XPS, and FTIR studies. The results suggest that the prepared CZTS by EC-ALD is an ideal deposit suitable for fabricating a thin film solar cell.5. Preparation of Cu2Se on p-type Si using combination of electroless deposition and EC-ALD thin films are grown onto p-Si (100) substrate using combination electroless and electro-deposition, which includes the elecdeposition of Cu2Se thin films upon the previous deposition of a conductive layer of Cu by electroless deposition. The obtained films were characterized by XRD, FE-SEM with an EDX analyzer, FTIR, and OCP studies. The results show the high quality of the Cu2Se film deposited compared to conventional electrodeposition method, and suggest that the combination of electroless and electro-deposition is an ideal method for deposition of compound semiconductor films on p-Si.6. Electrodeposition of Pt nanoparticles on carbon nanotubes-modified polyimide materials for electrocatalytic applicationsPt nanoparticles attached to the carbon nanotubes (CNTs)-modified polyimide (PIs) materials were successfully synthesized. FE-SEM and XPS were used to characterize this nanocomposite film, which has excellent stability and flexibility. The electrochemical study found that the Pt/PI/CNTs nanocomposite film exhibited remarkable electrocatalytic activity towards the oxidation of methanol and nitrite.