| Among semiconductor materials, Zinc sulfide(Zn S) is an important and with a band gap of about 3.7 e V wide direct band gap semiconductor material. It has been widely applied in optoelectronics and so on. By both of doping and thermal annealing can improve the physical and chemical properties of Zn S films. In doping, n-type doping of Zn S is of much importance, it can lay the foundation for the preparation of p-n junction in the future.In this study, variety of intrinsic and doped Zn S films was synthesized by CBD.The mechanism of the film growth was proposed and the microscopic structure and PL performances of the films were carefully emphatically through the test method.The main findings are listed as follows:(1) When using ammonia as complexing agent and p H value regulator, rapid thermal processing does not lead the amorphous Zn S films to crystallize. This shows that it is not good to use ammonia alone as complexing agent to synthesize crystalline Zn S films on silicon substrates by CBD. The particles of the films tends to obviously refine, and the distribution of the particle size becomes uniform, and the surface roughness decreases with increasing thermal treatment temperature(Trtt), which may be attributed to the rearrangement and growth of particles in the process of rapid thermal treatment. The absorption edge of the films tends to redshift with Trtt, which is attributed to the change in the film stress. Increasing the Trtt initially increases the number of point defects in the film, and then decreases the number of point defects due to the rearrangements of atoms in the film. It is worth to be noted that the luminescence peak associated with point defects almost disappeared at Trtt >300℃.(2) Due to the hydrolysis of Zn S, Zn O films rather than the desired Zn S were synthesized on heavily-doped p-type Si(100) substrates by CBD with triethanolamine as the complexing agent, and ammonia as the p H regulator. And the best-quality Zn S films were synthesized at p H value of 4 assisted with ethylenediamine as complexing agent.(3) Effect of ethylenediamine concentration on the properties of the product wasstudied by using ethylenediamine as complexing agent. The Zn S films are composed of the dominated cubic Zn S phases besides a small number of the hexagonal Zn S phases. The result is not reported previously. The agglomeration of the particles and uneven film surface are observed when without ethylenediamine. As ethylenediamine concentration increases, the film surface becomes increasingly smooth and compact,indicating that the complexing agent plays an important role in improvement of the film surface. The absorption edge of the films almost performs blueshift with increasing ethylenediamine concentration, and the blueshift of the absorption edge can be attributed to the influence of stress in Zn S thin films. The photoluminescence spectra of the films show a wide light-emitting band in the visible region that is related to the point defects in the film(zinc vacancies and sulfur vacancies).(4) Zinc ion concentration(CZn) of the precursor has a strong effect on the properties of Zn S films. The XRD spectrum almost show no clear Zn S characteristic diffraction peaks at CZn = 0.25 M. The possible reason is that it is difficult to generate Zn S film under this ion concentration, or the film is such poorly crystallized or may be amorphous. The crystallization of the Zn S films are clearly improved with increasing the CZn value.(5) The intrinsic Zn S film has a large electrical resistivity of 1.5×107 Ωcm that decreases to 4.2×102 Ωcm at the Al Cl3 mole = 1.0 mmol and then increases with the Al Cl3 mole. The initial decrease of the electrical resistivity with Al Cl3 mole is mainly related to the partial substitute for Zn2+ by Al3+ and enhanced crystallization. The former increases the free carrier concentration, while the latter increases the mobility of the free carriers. And the increase in resistivity can be attributed to the enhanced grain boundary scattering by Al3+. |
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