• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.18 no.2
• /
• pp.72-75
• /
• 2008

Zinc oxide (ZnO) thin films were prepared by a sol-gel method. The structural and electrical properties were investigated by varying drying and annealing temperatures. The thin films were coated (250 nm) by spin-coating method on glass substrates. The optimum drying temperature of ZnO thin films was 300$^{\circ}C$ where the resistivity was the lowest and the preferred c-axis orientation was the highest. The annealing was carried out in air and inert atmospheric conditions. The degree of the preferred c-axis orientation was estimated. The highest preferred c-axis orientation was recorded at 600$^{\circ}C$. The preferred c-axis orientation and grain growth resulted in the mobility enhancement of the ZnO thin films, and the lowest resistivity was 0.62${\Omega}{\cdot}cm$ at 600$^{\circ}C$.

• Journal of information and communication convergence engineering
• /
• v.3 no.3
• /
• pp.131-136
• /
• 2005

The effects of the deposition temperature on the growth characteristics of the ZnO films were studied for film bulk acoustic wave resonator (FBAR) device applications. All films were deposited using a radio frequency (RF) magnetron sputtering technique. It was found that the growth characteristics of the ZnO films have a strong dependence on the deposition temperature from 25 to $350^{\circ}C$. The ZnO films deposited below $200^{\circ}C$ exhibited reasonably good columnar grain structures with a highly preferred c-axis orientation while those above 200°C showed very poor columnar grain structures with a mixed-axis orientation. This study seems very useful for the future FBAR device applications.

• Journal of the Korean Ceramic Society
• /
• v.35 no.10
• /
• pp.1107-1112
• /
• 1998

We could obtan c-axis oriented $SrBi_2$$Ta_2$$O_9$ thin films on usual Pt(111)/Ti/$SiO_2$/Si(100) substrate using a r. f. magnetron sputtering technique. According to the increase of sputtering pressure from 250 to 300 mTorr the Bi content and degree of the c-a xis preferred orientation of $SrBi_2$$Ta_2$$O_9$ thin films were increased. By controlling Bi(or $Bi_2O_3$) loss from $SrBi_2$$Ta_2$$O_9$ thin films during post annealing and by inserting $Bi_2O_3$ layer in $SrBi_2$$Ta_2$$O_9$ thin films the effect of Bi content on the c-axis oriented growth of $SrBi_2$$Ta_2$$O_9$ thin films could be investigated without the effect of sputtering pressure. The degree of the c-axis preferred orientation of $SrBi_2$$Ta_2$$O_9$ thin films was increased with increasing with increasing Bi content by control of Bi(or $Bi_2O_3$) loss of $SrBi_2$$Ta_2$$O_9$ thin films. But the c-axis oriented growth of $SrBi_2$$Ta_2$$O_9$ thin films disappeared by the inserting of $Bi_2O_3$ lay-er in $SrBi_2$$Ta_2$$O_9$ thin films.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2003.05a
• /
• pp.88-92
• /
• 2003

In this paper, the characteristics of the ZnO films deposited on AI bottom electrode and the temperature effects on the ZnO film growth are presented along with the fabrication and their evaluation of the film bulk acoustic wave resonator (FBAR) devices. All the films used in this work were deposited using a radio-frequency (RF) magnetron sputtering technique. Growth characteristics of the ZnO films are shown to have a strong dependence on the deposition temperatures ranged from room temperature to 35$0^{\circ}C$ regardless of the RF power applied for sputtering the ZnO target. In addition, according to the growth characteristics of the distinguishably different micro-crystal structures and the degree of the c-axis preferred orientation, the deposition temperatures can be divided into 3 temperature regions and 2 critical temperatures in-between. Overall, the ZnO films deposited at/below 20$0^{\circ}C$ are seen to have columnar grains with a highly preferred c-axis orientation where the full width at half maximum (FWHM) of X-ray diffraction rocking curve is 14$^{\circ}$. Based on the experimental findings, several FBAR devices were fabricated and measured. As a result, the FBAR devices show return loss of ~19.5dB at resonant frequency of ~2.05GHz.

• The Korean Journal of Ceramics
• /
• v.6 no.2
• /
• pp.116-119
• /
• 2000

The a-axis and c-axis prefer oriented SBT thin films could be deposited on Pt(111)/Ti/$SiO_2$$650^{\circ}C$). The c-axis preferred orientation of SBT film can be obtained by Sr deficiency and high compressive stress. However, the a-axis-oriented grains can be formed under stoichiometric Sr content and nearly stress-free state.

• 한국초전도학회:학술대회논문집
• /
• v.10
• /
• pp.51-55
• /
• 2000

Using modified melt-textured grown targets, YBa$_2$Cu$_3$O$_{7-{\delta}}$ thin films were prepared by pulsed laser deposition technique at the laser energy density from 1 J/cm$_2$ to 4 J/cm$_2$. All the films showed c-axis preferred orientations, however, a-axis outgrowths on the film surface were considerably increased with an increase of the laser energy density. To examine the origin of the a-axis outgrowth formation, the microstructures of films deposited at 2 J/cm$_2$ and 4 J/cm$_2$ were investigated using X-ray diffraction, transmission electron microscopy, and high-resolution electron microscopy. It was shown that a significant number of Y$_2$O$_3$ inclusions were formed during the growth of c-axis oriented films at 4 J/cm$_2$. These inclusions formed nucleation sites for the a-axis outgrowths. It is considered that, due to the unstable growth conditions with a high flux density of incident vapor species and the strain induced by the surrounding c-axis films, the Y$_2$O$_3$ inclusions would prefer the nucleation of α-axis grains.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.7 no.2
• /
• pp.255-262
• /
• 2003

In this paper, an investigation on the ZnO film deposition using radio-frequency magnetic sputtering techniques on aluminum bottom electrode for film bulk acoustic wave resonator (FBAR) filter applications and the temperature effects on the ZnO film growth is presented. The investigation on how much impact the actual process temperature may have on the crystal growth is more meaningful if it is considered that the piezoelectricity property of ZnO films plays a dominant role in determining the resonance characteristics of FBAR devices and the piezoelectricity is determined by the degree of the c-axis preferred orientation of the deposited ZnO films. In this experiment, it was found that the growth of ZnO crystals has a strong dependence on the deposition temperature ranged from room temperature to $350^{\circ}C$ regardless of the RF powers applied and there exist 3 temperature regions divided by 2 critical temperatures according to the degree of the c-axis preferred orientation. Overall, below $200^{\circ}C$, ZnO deposition results in columnar grains with a highly preferred c-axis orientation. With this ZnO film, a multilayered FBAR structure could be realized successfully.

• Proceedings of the Korea Contents Association Conference
• /
• 2009.05a
• /
• pp.807-809
• /
• 2009

Thin film deposition methods have been widely used and intensively investigated because high quality crystalline films enable to fabricate by sputtering. Especially rf magnetron sputtering deposition has advantages of being employ a relatively high deposition rate and also to achieve high crystalline films in low pressure because plasma density around target by magnetic is high. To apply ZnO thin film for SAW filter, it has highly flat surface, excellent c-axis preferred orientation and high resistivity value. As-deposited ZnO films showed the strong c-axis growth and excellent crystallinity. C-axis preferred orientation, resistivity and surface roughness highly depended on oxygen/argon gas ratio.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.07a
• /
• pp.50-53
• /
• 2002

YMnO$_3$ thin films were spun-coated on the Pt/Ti/SiO$_2$/Si substrates by sol-gel process using alkoxides, and then dried on hot plates from 300 to 450 $^{\circ}C$. The prepared YMnO$_3$ thin films were annealed at 850 $^{\circ}C$ in O$_2$ atmosphere for 1 h. The crystallization of YMnO$_3$ thin films were improved to preferred c-axis orientation and the dielectric characteristics were progressed by increasing the drying temperature. The range of dielectric constant of thin film dried at 450 $^{\circ}C$ is 12.9-22.3 and close to that of YMnO$_3$ single crystal. The ferroelecrtic property of YMnO$_3$ thin film was observed on the YMnO$_3$ films. The maximum remnant polarization (2Pr) of YMnO$_3$ thin films dried at 450 $^{\circ}C$ was about 2.91 ${\mu}$ C/cm2. It was suggested that the drying temperature affect to the initial stage of thin film growth of preferred c-axis orientation.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.14 no.5
• /
• pp.187-192
• /
• 2004

We try to use isopropanol which has low boiling point to prepare ZnO thin films at low temperature. ZnO thin films were prepared by sol-gel spin-coating method using zinc acetate dehydrate-isopropanol-monoethanolamine (MEA) solution. The c-axis preferred orientation and optical properties of ZnO films with preheating temperature have been investigated. ZnO thin films were preheated at 200 to $300^{\circ}C$ with an interval of $25^{\circ}C$ and post-heated at $650^{\circ}C$. The ZnO film preheated at $275^{\circ}C$ and post-heated at $650^{\circ}C$ was highly oriented along c-axis (002) plane, and the surface with homogeneous and dense microstructures was formed having nano-sized grains. The optical transmittance was above 90 % in the visible range and exhibited absorption edges at 368 nm wavelength.