Chengtao Yang

EFFECTS OF ELECTRODEPOSITION CONDITIONS ON THE MICROSTRUCTURES OF ZNO THIN FILMS

ABSTRACT ZnO thin films were grown by cathodic deposition on indium tin oxide (ITO)-covered glass substrates from a simple aqueous zinc nitrate solution. Cyclic voltammetry (CV) experiments were performed to verify the reaction mechanism. X-ray diffraction measurements indicated that the as-grown films were of hexagonal wurtzite structure. The influence of the electrodeposition conditions and the post-heating on the microstructures of the polycrystalline ZnO thin films was investigated by SEM and AFM observations. The microstructures of the ZnO thin films could be improved by annealing treatment. The films obtained at 0.1 M Zn(NO3), −0.9 V potential and 65°C were compact, homogeneous and (002) oriented, and the average deposition rate can be evaluated to be 2 μm/h.

Characterization of Pb(Zr,Ti)O3 thin film prepared by pulsed laser deposition

Abstract The PZT thin film has been successfully prepared on Pt/Ti/SiO2/Si substrate by pulsed laser deposition. The target is of Pb(Zr052Ti0.48)O3 which has excess Pb. The PZT thin film thickness is between 200 and 500 nm while the buffer layer Ti is of 50 nm thick. This paper describes the effects of deposition temperature on the crystallization process of sputtering PZT film. X-ray diffraction (XRD) and atomic force microscopy (AFM) showed the crystalline structure, the surface morphology and the crystallographic orientations of PZT films. For electrical characterizations, the bottom electrode with width of 1.0 mm strip was formed by depositing the Ti/Pt on Si substrate and etching, the top electrode with same shape and width was formed by sputtering Pt but it was at right angles to the bottom electrode, so the ferroelectric capacitor had an area of 1.0×10−2 cm2. Ferroelectric properties of the capacitor has been characterized using a ferroelectric film tester (Radiant Technologies, RT66A). Process optimized PZT film has a coercive field of 45 kV cm−1 and a remanent polarization of 25 μC cm−2. The PZT film has perovskite structure.

Effects of sputtering atmosphere on the properties of c-plane ScAlN thin films prepared on sapphire substrate

In this work, scandium aluminum nitride alloy (ScAlN) thin films were prepared on c-sapphire substrates by DC reactive magnetron sputtering with a scandium aluminum alloy (Sc0.06Al0.94) target. The crystal orientation and surface morphology were detected by XRD and AFM, respectively. The electrical properties were analyzed by a standard ferroelectric test system and piezoelectric response force microscopy. The results show that the sputtering atmosphere, including N2/Ar flow ratio and sputtering pressure, appears to be important to influence the crystal quality and electrical properties of ScAlN films. With the N2/Ar flow ratio increasing from 3.1:7 to 3.6:7, the crystal orientation and surface morphology of ScAlN films firstly improves and then gets worse. Meanwhile, the electrical qualities of the films performs a similar variation. When the sputtering pressure increases from 0.3 to 0.7xa0Pa, the properties of the films change obviously too, and the best sputtering pressure is determined as 0.5xa0Pa. Finally, highly c-axis ScAlN films can be obtained with a N2/Ar flow ratio of 3.4:7 and a sputtering pressure of 0.5xa0Pa, and the FWHM value of the rocking curve, the RMS roughness, the resistivity, the dielectric constant ɛr and piezoelectric constant d33 are 2.6°, 2.650xa0nm, 2.9xa0×xa01012xa0Ω/cm, 12.2 and 8.1xa0pC/N, respectively.

The preparation of ScAlN(002) alloy thin films deposited on Si(100) substrates by DC reactive magnetron sputtering

Scandium aluminum nitride (ScAlN) alloy thin films were deposited on (100) silicon substrates by DC reactive magnetron sputtering method using a scandium aluminum alloy (Sc0.06Al0.94) target. The influences of N2/Ar-flow ratio, substrate temperature, sputtering power and sputtering pressure on the film’s crystal orientation and surface morphology were investigated systematically. The c-axis preferred orientation degree changes obviously, firstly increasing to the maximum and then decreasing, with increasing each of the sputtering parameters. Meanwhile, the surface morphology of ScAlN films performs a similar variation. Then, the relationship between the crystal orientation and piezoelectric response is determined. Finally, it is demonstrated that highly c-axis oriented ScAlN thin films, with FWHM value of the rocking curve of 2.9°, RMS roughness of 2.612xa0nm and piezoelectric constant d33 of 8.9xa0pC/N, can be obtained with a N2/Ar-flow ratio of 3.3:7, a substrate temperature of 650xa0°C, a sputtering power of 130xa0W and a sputtering pressure of 0.5xa0Pa.

Influence of B2O3/SiO2 Ratio on the Fabrication of Nd:YAG Ceramics

B2O3/SiO2 are used as composite sintering aids to fabricate Nd:YAG ceramics by solid-state reaction and vacuum sintering method at 1750°C for 5h using Nano-Al2O3, Y2O3, Nd2O3 as starting materials. In this article, we focus on the influence of B2O3/SiO2 ratio on grain size, porosity and relative density. Finally, with the increase of B2O3/SiO2 ratio, the density and shrinkage rate of transparent ceramics increase, the grain size becomes uniform and the porosity reduces, for the reason that B3+ begins to vaporize at 1300°C and is reduced to trace levels by 1600°C. The best B2O3/SiO2 ratio is 4: 1.

Preparation of ScAlN films as a function of sputtering atmosphere

Sc doped AlN films were deposited by dc reactive magnetron sputtering on (100) p-type silicon substrates mixed with Ar–N2 gas atmosphere. It is appropriate for a wide variety of applications for the excellent piezoelectric properties, which closely depends on their crystal structures and morphological properties. In this paper, we research the influence of sputtering atmosphere including nitrogen proportion from 30 to 60xa0% and pressure from 0.4 to 0.8xa0Pa on sputtering rate, crystal quality and electric properties. It indicated that the sputtering rate strongly relied on the condition atmosphere, decreasing with increasing of pressure and nitrogen proportion. The best c-axis oriented ScAlN film could be prepared at low pressure of 0.4xa0Pa and reasonable nitrogen proportion of 35xa0%, presenting full width at half maximum of 1.7°. Moreover, the results found that the electric properties are demonstrated closely depending on the crystal quality, too.

GROWTH AND CHARACTERIZATION OF PZT FILMS WITH DIFFERENT GRAIN SIZES

ABSTRACT Pb(Zr0.55Ti0.45)O3 (PZT) thin films with different grain size have been fabricated by controlling the post-annealing process. PZT thin films nucleated at 550°C and the grains began growing above 650°C. Long nucleation process time but relatively short growth process time resulted in small grain. In contrast, long growth process time but short nucleation process time resulted in large grain size. PZT thin films with different grain size show different electrical properties. The polarization increases with the increase of grain size. However, the coercive field exhibites a paraboliclike relationship with grain size. The coercive field increases with the increase of grain size below 70 nm, whereas decreases as the grain size increases above 70 nm. The grain size of 70 nm is thought to be the critical size for the domain structure transition. While increasing the grain size, PZT thin films experience a transition from single domain state to multi domain state, which is related to the polarization switching. It is well known that the polarization of ferroelectric thin films with multi domain structure switches much easier than that with single domain structure. Obviously, the coercive field dependence on the grain size is interpreted.

STRUCTURE AND FERROELECTRIC PROPERTIES OF PZT THIN FILM DEPOSITED ON LaNiO3 BOTTOM ELECTRODES

ABSTRACT In this paper, highly oriented conductive LaNiO3(LNO) thin films have been deposited on LaAlO3(LAO), SrTiO3(STO), MgO and Pt/Ti/SiO2/Si substrates by pulsed laser deposited(PLD). The AFM images and surface morphology of LNO electrode deposited on LAO, STO, SiO2/Si and MgO substrate have been measured. The particle size of the LNO on different substrates has been obtained. Pb(Zr0.52Ti0.48)O3(PZT) thin films were prepared by RF sputtering on LNO electrode deposited on different substrates. The structure and electrical properties of PZT ferroelectric films deposited on LNO electrode have been studied.

INFLUENCE OF DEPOSITION TEMPERATURE AND N2 FLOW RATE ON HIGH QUALITY ZNO THIN FILM DEPOSITED ON SiO2/SI SUBSTRATE BY ULTRASONIC SPRAY PYROLYSIS

ABSTRACT ZnO thin films were prepared on SiO2/Si substrate by ultrasonic spray pyrolysis (USP) method using the aqueous solution of zinc acetate dehydrate. X-ray diffraction (XRD) and atomic force microscopy (AFM) were employed to analyze the crystalline and microscopic structure of the films. The properties of ZnO films were investigated with respect to deposition temperature (Ts) and N2 flow rate (f). The results show that ZnO thin films exhibit hexagonal wurtzite structure and the highly preferential orientation along c-axis under Ts = 320°C and f = 5 L/min deposition condition.

Preparation of (100) oriented Sc-doped AlN film on flexible substrate under different pressures using RF reactive sputtering

Abstract Sc-doped AlN films with (100) orientation have high surface acoustic wave velocity and excellent optical properties. Sc-doped AlN thin films based on flexible substrate were prepared by RF reactive magnetron sputtering at pressure levels ranging from 0.3 Pa to 1.5 Pa. The sputtering rate, crystal quality, and electric properties of the Sc-doped AlN films were investigated. The results show that pressure greatly influences the preparation of Sc-doped AlN thin films. Under low pressure, (002) oriented Sc-doped AlN film was prepared; with increasing pressure, the fraction of the (100) plane increased. Furthermore, the electrical properties were closely related to the crystal quality, achieving a maximum resistivity of 3.5 × 1012 Ω · cm, a minimum leakage current of 0.65 × 10−8 A, and a maximum piezoelectric response of 5.2 pC · N−1.