The effects of oxygen partial pressure on local structural properties for Ga-doped ZnO thin films

We report on Raman scattering studies of Ga-doped ZnO thin films that were grown by intentionally changing oxygen partial pressure in order to study the influences of oxygen partial pressure on local structural properties of this material. Raman spectra of ZnO:Ga (3 wt.% Ga-doped) films revealed vibrational modes at 575 and 630–660 cm^− 1 in addition to the host phonons of ZnO. These additional modes correspond to local vibrational modes associated with oxygen vacancy (V_O) and Ga impurity (Ga_Zn), respectively. With increasing oxygen partial pressure (oxygen flow rate up to ∼ 10 sccm), the 575-cm^− 1 mode decreases in its intensity, indicating the reduced V_O concentration. Further increasing oxygen partial pressure (> 10 sccm), we find a substantial disorder apparent in host ZnO phonons and some additional modes. These results suggest that the oxygen-rich condition may cause the formation of compensating-defects such as oxygen interstitials (O_i), Zn vacancy (V_Zn) and their complexes (Ga_Zn–O_i, Ga_Zn–V_Zn), strongly reducing carrier concentration in this system.     

Effect of oxygen partial pressure on the structural and optical properties of sputter deposited ZnO nanocrystalline thin films

We report the influence of deposition parameters such as oxygen partial pressure and overall sputtering pressure on the structural and optical properties of the as-grown ZnO nanocrystalline thin films. The films were prepared by dc magnetron sputtering using Zn metal target under two different argon and oxygen ratios at various sputtering pressures. Microstructure of the films was investigated using X-ray diffraction and scanning electron microscopy. Optical properties of the films were examined using UV-Visible spectrophotometer. The results show that the films deposited at low oxygen partial pressure (10%) contain mixed phase (Zn and ZnO) and are randomly oriented while the films deposited at higher oxygen partial pressure (30%) are single phase (ZnO) and highly oriented along the c-axis. We found that the oxygen partial pressure and the sputtering pressure are complementary to each other. The optical band gap calculated from Tauc's relation and the particle size calculation were in agreement with each other.     

Effect of the oxygen pressure on the photoluminescence properties of ZnO thin films by PLD

ZnO thin films on Si(111) substrate were deposited by laser ablation of Zn target in oxygen reactive atmosphere; Nd-YAG laser with wavelength of 1064 nm was used as laser source. The experiments were performed at laser energy density of 31 J/cm², substrate temperature of 400 °C and various oxygen pressures (5–65 Pa). X-ray diffraction was applied to characterize the structure of the deposited ZnO films and the optical properties of the ZnO thin films were characterized by photoluminescence with an Ar ion laser as a light source using an excitation wavelength of 325 nm. The influence of the oxygen pressure on the structural and optical properties of ZnO thin films was investigated. It was found that ZnO film with random growth grains can be obtained under the condition of oxygen pressure 5–65 Pa. It will be clearly shown that the grain size and the formation of intrinsic defects depend on the oxygen partial pressure and that high optical quality of the ZnO films is obtained under low oxygen pressure (5 Pa, 11 Pa) conditions.     

氧分压对掺钼氧化铟透明导电薄膜光电性能的影响

采用射频磁控反应溅射法在k9玻璃衬底上制备了In2O3∶Mo(IMO)透明导电薄膜,分析了不同氧分压条件下IMO薄膜的晶体结构、化学成分及光电性能.结果表明:不同氧分压下制备的IMO薄膜具有不同晶粒的取向性;随着氧分压的增加,薄膜的载流子浓度、载流子迁移率先增加后减小;薄膜的电阻率呈现先增加再减少然后再增加的趋势.在可...     

Dependence of the resistivity and the transmittance of sputter-deposited Ga-doped ZnO films on oxygen partial pressure and sputtering temperature

Ga-doped ZnO (GZO) thin films were prepared by rf magnetron sputtering and dependence of the electrical resistivity and the transmittance of the GZO films on the oxygen partial pressure (R = the O₂/Ar gas flow ratio) and the substrate temperature were investigated. The resistivity of the GZO film decreases first and then increases with an increase in the substrate temperature (T). A minimum resistivity obtained with a substrate temperature of 300 °C is 3.3 × 10⁻⁴ Ωcm. The resistivity nearly does not change with R for R < 0.25. The decrease in the resistivity for R < 0.25 is attributed to enhancement in crystallinity, whereas the increase in the resistivity for R > 0.25 to precipitation of gallium oxides at grain boundaries. Optical transmittance of the GZO films is enhanced by increasing R up to 0.75. This enhancement in the transmittance is due to a decrease in oxygen vacancy concentration and a decrease in surface roughness with R.     

Effect of the oxygen partial pressure on the microstructure and optical properties of ZnO:Cu films

Cu-doped zinc oxide (ZnO:Cu) films were deposited on Si substrates using radio frequency reactive magnetron sputtering at different oxygen partial pressures. The effect of oxygen partial pressure on the microstructures and optical properties of ZnO:Cu thin films were systematically investigated by X-ray diffraction (XRD), atomic force microscopy (AFM) and fluorescence spectrophotometer. The results indicated that the grain orientation of the films was promoted by appropriate oxygen partial pressures. And with increasing oxygen partial pressure, the compressive stress of the films increased first and then decreased. The photoluminescence (PL) of the samples were measured at room temperature. A violet peak, two blue peaks and a green peak were observed from the PL spectra of the four samples. The origin of these emissions was discussed and the mechanism of violet emission of ZnO:Cu thin films were suggested.     

Influence of oxygen partial pressure on the structure and photoluminescence of direct current reactive magnetron sputtering ZnO thin films

The effects of oxygen partial pressure on the structure and photoluminescence (PL) of ZnO films were studied. The films were prepared by direct current (DC) reactive magnetron sputtering with various oxygen concentrations at room temperature. With increasing oxygen ratio, the structure of films changes from zinc and zinc oxide phases, single-phase ZnO, to the (002) orientation, and the mechanical stresses exhibit from tensile stress to compressive stress. Films deposited at higher oxygen pressure show weaker emission intensities, which may result from the decrease of the oxygen vacancies and zinc interstitials in the film. This indicates that the emission in ZnO film originates from the oxygen vacancy and zinc interstitial-related defects. From optical transmittance spectra of ZnO films, the plasma edge shifts towards the shorter wavelength with the improvement of film stoichiometry.     

Effects of oxygen pressure on the structure and photoluminescence of ZnO thin films

A series of ZnO thin films were deposited on silicon (100) substrate at 473 K by using facing target RF magnetron sputtering system at different oxygen pressure in this paper. The structure, surface morphology and photoluminescence of the ZnO thin films were characterized by X-ray diffraction, atomic force microscopy (AFM), and photoluminescence spectra (PL), respectively. The results showed that only a (002) peak of hexagonal wurtzite appeared in all ZnO thin films, indicating that ZnO films exhibited strong texture. With increasing the oxygen pressure, the results indicated that the ZnO film deposited at 1.2 Pa Ar pressure and 0.6 Pa oxygen pressure had the best preferential C-axis orientation and the weakest compressive stress. Meanwhile, AFM observation showed that ZnO film deposited at pure Ar had the highest surface roughness. With the increment of oxygen pressure, the surface roughness decreased gradually. In addition, PL measurement showed that the ZnO film deposited at 1.2 Pa Ar pressure and 0.6 Pa oxygen pressure had the strongest ultraviolet emission and the weakest blue emission.     

Interplay of the influence of oxygen partial pressure and rf power on the properties of rf-magnetron-sputtered AZO thin films

The complex interplay between the influence of oxygen partial pressure and that of rf power on the structural, electrical and optical properties of rf-magnetron-sputtered aluminium-doped zinc oxide, AZO, thin films is illustrated. The dependence of film electrical resistance and interplanar spacing of film crystallites on rf power seems to be different at higher oxygen partial pressure values than at lower ones. Film preparation was performed at room temperature (without extra heating) and low pressure p \(=\) 0.5 mTorr, varying the rf power density between P \(=\) 0.57 and 2.83 W \(\hbox {cm}^{-2}\) at different relative oxygen partial pressure values. An explanation of film properties has been sought in terms of changes in the chemical properties of the films due to the bombardment of the films during film formation with negative oxygen ions.     

The effects of oxygen partial pressure on BST thin films deposited on multilayered bottom electrodes

Ba_0.5Sr_0.5TiO₃ (BST) thin films have been deposited by r.f. magnetron sputtering on silicon and platinum-coated silicon substrates with different buffer and barrier layers. BST films deposited on Si/SiO₂/SiN/Pt and Si/SiO₂/Ti/TiN/Pt multilayer bottom electrode have been used for the fabrication of capacitors. XRD and SEM studies were carried out for the films. It was found that the crystallinity of the BST thin film was dependent upon oxygen partial pressure in the sputtering gas. The role of multilayered bottom electrode on the electrical properties of Ba_0.5Sr_0.5TiO₃ films has been also investigated. The dielectric properties of BST films were measured. The results show that the films exhibit pure perovskite phase and their grain sizes are about 80–90 nm. The dielectric properties of the BST thin film on Si/SiO₂/Ti/TiN/Pt electrode was superior to that of the film grown on Si/SiO₂/SiN/Pt electrode.     

Effect of oxygen pressure on the structural and optical properties of ZnO thin films on Si (111) by PLD

ZnO thin films were grown on Si (111) substrates by pulsed laser deposition (PLD) at various oxygen pressures in order to investigate the structural and optical properties of the films. The optical properties of the films were studied by photoluminescence spectra using a 325 nm He-Cd laser. The structural and morphological properties of the films were investigated by XRD and AFM measurements, respectively. The results suggest that films grown at 20 Pa and 50 Pa have excellent UV emission and high-quality crystallinity. The research of PL spectra indicates that UV emission is due to excitonic combination, the green band is due to the replacing of Zn in the crystal lattice for O and the blue band is due to the O vacancies.     

O2气流量对MOCVD法生长ZnO薄膜性质的影响

采用低压MOCVD方法,在(0001)Al2O3衬底上沉积了ZnO薄膜.研究了Ⅵ族源O2气流量的变化对薄膜结构、表面形貌及光致发光特性的影响.增加O2气流量,ZnO薄膜结晶质量有所降低,半高宽从0.20°展宽至0.30°,由单一c轴取向变成无取向薄膜.同时,生成的柱状晶粒平均尺寸减少,晶粒更加均匀,均方根粗糙度减小.PL谱分析表明随O2气流量加大,带边峰明显增强,深能级峰明显减弱,ZnO薄膜光学质量提高.这些事实说明在本实验条件下,采用低压MOCVD方法生长的ZnO薄膜在光致发光特性主要依赖于Zn、O组份配比,而不是薄膜的微观结构质量.     

Effects of thermal annealing in oxygen plasma for buffer layers on properties of ZnO thin films

ZnO thin films with ZnO buffer layers were grown by plasma-assisted molecular beam epitaxy (PA-MBE) on p-type Si(100) substrates. Before the growth of the ZnO thin films, the ZnO buffer layers were deposited on the Si substrates for 20 minutes and then annealed at the different substrate temperature ranging from 600 to 800 degrees C in oxygen plasma. The structural and optical properties of the ZnO thin films have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and room-temperature (RT) photoluminescence (PL). A narrower full width at half maximum (FWHM) of the XRD spectra for ZnO(002) and a larger grain are observed in the samples with the thermal annealed buffer layers in oxygen plasma, compared to those of the as-grown sample. The surface morphology of the samples is changed from rugged to flat surface. In the PL spectra, near-band edge emission (NBEE) at 3.2 eV (380 nm) and deep-level emission (DLE) around 1.77 to 2.75 eV (700 to 450 nm) are observed. By increasing the annealing temperatures up to 800 degrees C, the PL intensity of the NBEE peak is higher than that of the as-grown sample. These results imply that the structural and optical properties of ZnO thin films are improved by the annealing process.     

Effect of oxygen partial pressure on microstructural and optical properties of titanium oxide thin films prepared by pulsed laser deposition

Nanocrystalline titanium oxide (TiO₂) thin films were deposited on silicon (1 0 0) and quartz substrates at various oxygen partial pressures (1 × 10⁻⁵ to 3.5 × 10⁻¹ mbar) with a substrate temperature of 973 K by pulsed laser deposition. The microstructural and optical properties were characterized using Grazing incidence X-ray diffraction, atomic force microscopy, UV–visible spectroscopy and photoluminescence. The X-ray diffraction studies indicated the formation of mixed phases (anatase and rutile) at higher oxygen partial pressures (3.5 × 10⁻² to 3.5 × 10⁻¹ mbar) and strong rutile phase at lower oxygen partial pressures (1 × 10⁻⁵ to 3.5 × 10⁻³ mbar). The atomic force microscopy studies showed the dense and uniform distribution of nanocrystallites. The root mean square surface roughness of the films increased with increasing oxygen partial pressures. The UV–visible studies showed that the bandgap of the films increased from 3.20 eV to 3.60 eV with the increase of oxygen partial pressures. The refractive index was found to decrease from 2.73 to 2.06 (at 550 nm) as the oxygen partial pressure increased from 1.5 × 10⁻⁴ mbar to 3.5 × 10⁻¹ mbar. The photoluminescence peaks were fitted to Gaussian function and the bandgap was found to be in the range ∼3.28–3.40 eV for anatase and 2.98–3.13 eV for rutile phases with increasing oxygen partial pressure from 1 × 10⁻⁵ to 3.5 × 10⁻¹ mbar.     

氧分量对柔性衬底上WOx薄膜性能的影响

通过射频磁控溅射方法,在柔性PET衬底上低温沉积电致变色WOx薄膜.利用X射线衍射(XRD)、紫外-可见光分光光度计、X射线光电子能谱(XPS)分析所制备薄膜的微观结构、透光率、O元素的结合状态.结果表明,各氧分量下制备的WOx薄膜均为非晶态;氧分量0时制备的薄膜着、退色态透光率变化范围达到25%左右,具有较好的电致变色性能;XPS分析表明氧分量8%时氧空位含量最低,随着氧分量的继续增大,氧空位含量也增大.     

Behavior of dual ion beam sputtered MgZnO thin films for different oxygen partial pressure

Mg-doped ZnO (MgZnO) films were grown on p-Si (001) substrates by dual ion beam sputtering deposition system at a constant growth temperature of 600 °C for different oxygen partial pressure. The impact of oxygen partial pressure on the structural, electrical, elemental and morphological properties was thoroughly investigated. X-ray diffraction (XRD) spectra revealed that the deposited MgZnO films were polycrystalline in nature with preferred (002) crystal orientation. The peak of MgZnO (101) plane was reduced significantly as oxygen partial pressure was increased and disappeared completely at 80 and 100 % O₂. The maximum electron concentration was evaluated to be 5.79 × 10¹⁸ cm^?3 with resistivity of 0.116 Ω cm and electron mobility of 9.306 cm²/V s at room temperature, for MgZnO film grown with 20 % O₂. Raman spectra shows a broad peak at 434 cm^?1 corresponded to E ₂ ^high phonons mode of MgZnO wurtzite structure. The peak at 560 cm^?1 corresponded to the E₁ (LO) mode and was associated with oxygen deficiency in MgZnO films. Raman intensity at 560 cm^?1 reduced, on increasing oxygen partial pressure. A correlation between structural, electrical, elemental and morphological properties with oxygen partial pressure was also established.     

衬底和氧分压对Cu掺杂ZnO薄膜的结构及光学特性的影响

采用射频磁控溅射方法在玻璃和硅(100)衬底上制备了不同氧分压的Cu掺杂ZnO(ZnO∶Cu)薄膜。利用X射线衍射(XRD)、原子力显微镜(AFM)和光致荧光发光(PL)等表征技术,研究了衬底和氧分压对ZnO∶Cu薄膜的结晶性能和光学特性的影响。结果显示薄膜沉积在Si衬底上比玻璃衬底上有更好c轴择优取向,两种衬底上沉积的薄膜有相同的氧分压结晶规律,且在氧氩比为10∶10时,薄膜c轴取向同时达到最好。通过对光致发光的研究表明,在低氧环境时玻璃衬底较容易制得好的发光薄膜,可在富氧环境时Si衬底上制得的薄膜发光性能较好。     

Dependency of oxygen partial pressure on the characteristics of ZnO films grown by radio frequency magnetron sputtering

The effects of oxygen and argon gas contents on the structural and optical properties of epitaxially grown ZnO thin films on sapphire substrates by radio frequency magnetron sputtering were investigated. The growth rate of ZnO thin film decreases with increase in oxygen gas contents in the gas mixture. The high-resolution x-ray diffraction $ {\left( {10\overline{1} 2} \right)} $ rocking curve and plane-view transmission electron microscopy investigations reveal the presence of a reduced dislocation density in the ZnO thin films with decrease in oxygen/argon flow ratio. However, large density of defects were observed in the boundaries and inside of the micro-hillocks formed on the surface of ZnO thin film grown with pure argon. The increase in oxygen gas ratio resulted in the improvement of optical properties with suppression and red-shift of the deep level emission.     

Influence of oxygen pressure on structural,optical and magnetic properties of pure ZnO films

In this paper, we study the influence of oxygen pressure on structural, optical and magnetic properties of pure ZnO films. The chemical compositions and thickness of the film were estimated by Rutherford backscattering spectrometry measurements. X-ray diffraction patterns show all the films are in single phase and preferred along (002) orientation. With an increase of oxygen pressure, grain growth and average root mean square roughness is found to be increased. It is found that the intensity of UV emission peak increases whereas visible emission peak decreases in intensity with an increase of oxygen pressure. From the magnetization measurements, it is observed that ZnO film grown without oxygen pressure shows an enhanced ferromagnetic behaviour than that of the films grown with oxygen pressure of 0.05 and 0.1 mbar.