| Non-equilibrium state refers to the uneven phenomenon of the physical properties of each part of system (such as flow rate, temperature, density). Non-equilibrium state in this article refers to the process of thin film growth is non-equilibrium, the film growth process that is collision between various particles, reflection and adsorption between the particles and the substrate, nucleation and growth on the substrate, synthesis and consolidation and growth of the island-shaped and finally formation of the continuous film can be seen to conduct in the non-equilibrium. In recent years, thin films and thin film technology develop rapidly and various kinds of new thin-film materials spring up. Film production and microfabrication technology is continuously innovating. ZnO thin film material is widely used in a large number of thin film materials. It is a good wide band-gap of Ⅱ-Ⅵ race n-type semiconductor material,and its exciton binding energy is as high as60MeV, and it is easy to achieve efficient stimulated emission at room temperature. At room temperature its stable phase is a hexagonal structure, usually has a (002) orientation growth. The raw material of ZnO is inexpensive, nontoxic, stable performance, and easy to get. ZnO is one of the most potential for developping of new functional materials and is widely used in surface acoustic wave devices, solar cell electrodes, piezoelectric devices, gas sensors, magneto-optical devices, electro-optical devices, new luminous materials, buffer layers and other fields. Because the physical and chemical properties of ZnO thin films is very excellent and the ZnO doping makes the physical and chemical properties of ZnO films become more excellent, so recently the number of people that study the ZnO doping is increasing.Doping with different atom or ion in ZnO thin films will change the structure and band width of ZnO, and make ZnO thin film produce new phase, resulting in different physical and chemical properties.In this paper, we prepare the high-quality doped ZnO thin films using the radio frequency (RF) magnetron sputtering technique on silicon substrates and quartz glass substrates, and use variety of analytical methods to study their structure, surface morphology properties. The main contents of this paper are as follows:Firstly,We studied the impact of Er/Yb/Al doped-ZnO thin films with different amount to crystal structure and surface morphology. The results show that that Er-doped ZnO thin films prepared on silicon by RF magnetron sputtering have a high degree of C-axis preferred orientation., but C-axis orientation of Er/Yb/Al-doped ZnO films prepared under the same conditions are disappeared and become polycrystalline nanometer thin film with (102) oriented growth. XRD tests also showed that the grain size of the Er/Yb/Al-doped ZnO thin films decreases with the increase of Er element content, and it illustrates that the doped Er elements can make the grain size become small. AFM test showed that roughness of Er/Yb/Al-doped ZnO thin films is generally high at room temperature, and the quality of the film is not good. This illustrates that doping of Er3+, Yb3+, Al3+causes the change of crystal field of the ZnO film, and makes ZnO thin films deviate from the normal growth. Sample’s gray-scale becomes smaller slowly with the increasing of Er element, the average roughness and rms roughness are also reduced. It is consistent with the XRD results.Secondly, we studied the impact of the ratio of oxygen and argon to structure and surface morphology of Er-doped ZnO thin film. We analysis of the structure and crystallization of the sample film with X-ray diffraction, the result indicates that Er-doped ZnO thin films prepared on silicon and quartz glass substrate have a high degree of C-axis preferred orientation. As the oxygen partial pressure increased, the film’s (002) diffraction intensity is getting smaller and smaller, the value of FWHM become small at first and then large. When the oxygen and argon is in the ratio of4:16, FHWM is minimum and the film grain is the largest. According to analysis of the intensity of diffraction peaks and the film grain size, the optimum growth conditions of Er-doped ZnO films should be ratio of oxygen argon from0:16to4:16, and the ratio is estimated at2:16nearby. The atomic force microscope test results show that with increasing of oxygen partial pressure, the film surface roughness become bigger. Although the surface roughness of the film is smallest when the oxygen and argon is in the ratio of0:16, the particles size in the sample is variable and between the sample have a lot of holes particles and the particles. Leading to oxygen can reduce this phenomenon, and the result is consistent with tne analysis of X-ray diffraction. Atomic force microscopy analysis also showed that the surface of our thin film samples that we prepared is a Gaussian random surface.Finally, we analyze the influence of substrate temperature to the structure and surface morphology of Er-doped ZnO thin film. By X-ray diffraction we analysis the structure and crystallization of the sample films, the result indicates that Er-doped ZnO thin films prepared on silicon and quartz glass substrate have a high degree of C-axis preferred orientation. With the rising of the substrate temperature, the diffraction intensity of the film is getting higher and higher. The grain become larger at first and then become small and the maximum value is at400℃. With the increasing of temperature, film lattice constant tends to the standard lattice, and internal stress is reduced also. The atomic force microscope test results show that with increasing of temperature, the film surface roughness become smalle at first,and then become large.The minimum is at200℃and the maximum is at room temperature. The change of the grain of the film is consistent with the roughness.With rising of temperature internal defects and the boundary dense and uniformity of the film becomes more and more good. At400℃, thin film grow into film with low of internal defects density, good of boundary dense, large of grain size and good of uniformity. It is consistent with the X-ray diffraction analysis. Atomic force microscopy analysis also showed that the surface of our thin film samples that we prepared is a Gaussian random surface. |
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