Effects Of Post-annealing Temperature Research Articles

High mobility indium free amorphous oxide thin film transistors

High mobility bottom gate thin film transistors (TFTs) with an amorphous gallium tin zinc oxide (a-GSZO) channel layer have been produced by rf magnetron cosputtering using a gallium zinc oxide (GZO) and tin (Sn) targets. The effect of postannealing temperatures (200, 250, and 300°C) was evaluated and compared with two series of TFTs produced at room temperature (S1) and 150°C (S2) during the channel deposition. From the results, it was observed that the effect of postannealing is crucial for both series of TFTs either for stability as well as for improving the electrical characteristics. The a-GSZO TFTs (W∕L=50∕50μm) operate in the enhancement mode (n-type), present a high saturation mobility of 24.6cm2∕Vs, a subthreshold gate swing voltage of 0.38V/decade, a turn-on voltage of −0.5V, a threshold voltage of 4.6V, and an Ion∕Ioff ratio of 8×107, satisfying all the requirements to be used as active-matrix backplane.

Ferroelectric and piezoelectric properties of 0.948(K0.5Na0.5)NbO3–0.052LiSbO3 lead-free piezoelectric thick film by aerosol deposition

Lead-free, piezoelectric thick films of 0.948(K0.5Na0.5)NbO3–0.052LiSbO3 were fabricated by aerosol deposition and the effect of postannealing temperature on the dielectric, ferroelectric, and piezoelectric properties was investigated. The thickness of the films ranged from 5to17μm and highly dense films were obtained after deposition at room temperature. With increasing annealing temperature, the dielectric and ferroelectric properties were markedly increased. The maximum ferroelectric and dielectric properties of ε3T∕ε0=1012, Pr=15.5μC∕cm2, and d33=50pm∕V were obtained after annealing at 800°C for 1h. Above this temperature, the film exhibited rapid property degradation as it was decomposed due to Na2O evaporation.

Effect of post-annealing temperature on the microstructure and magnetic properties of Ce:YIG thin films deposited on Si substrates

Amorphous Ce1Y2Fe5O12 (Ce:YIG) thin films deposited on single crystal Si(100) and thermally oxidized Si(100) substrates by pulsed laser deposition were annealed in the temperature range of 700–1000°C in air. The annealing temperature dependence of microstructure and magnetic properties of Ce:YIG films was studied using X-ray diffraction combined with vibrating sample magnetometer. The results show that single phase of polycrystalline Ce:YIG thin films can be obtained by the post-annealing of as-deposited films at the temperature of 700°C. However, two steps of phase segregation of Ce:YIG occur as the post-annealing temperature increases: at first, Ce:YIG is decomposed into YIG and non-magnetic CeO2 when annealed at 800°C; then YIG continues to be decomposed forming Fe2O3 when the temperature is increased up to 900°C. Consequently, the saturation magnetization of Ce:YIG films decreases first and then increases with the post-annealing temperature going up, which indicates that the saturation magnetization of Ce:YIG films is mainly related to the phase composition of the films. Meanwhile, the presence of SiO2 buffer layer can significantly enhance the saturation magnetization of Ce:YIG films.

Microstructure and electrical properties of Ho-doped BaTiO3-sputtered films

The holmium-doped 200-nm-thick BaTiO3 (BT) thin films were prepared by rf magnetron sputtering. The effects of postannealing temperature and dopant concentration on microstructure and electrical properties were studied. Compositions of thin films studied are BT1 (Ba∕Ti=0.8543), BT (Ba∕Ti=0.9681), BT–0.05Ho, BT–1.1Ho, and BT–1.8Ho, and BT–2.9Ho where Ho content is in at %. For all films studied, the dielectric constant increases with increasing annealing temperature up to 700 °C due to better crystallinity and large grain sizes. The BT1 film annealed at 700 °C shows a high dielectric constant of 287 measured at 100 kHz and the Ho-doped film exhibited a dielectric constant of 135 for BT–1.1Ho annealed at 700 °C. A significant role of the Ho on the reduction of leakage current density is observed for the 700 °C annealed samples because of the smooth surface roughness. The BT–2.9Ho film shows the low leakage current density of 1.27×10−8A∕cm2 at an electric field of 100kV∕cm.

Effects of post-annealing temperature on structural, optical, and electrical properties of ZnO and Zn1−xMgxO films by reactive RF magnetron sputtering

ZnO and Zn1−xMgxO thin films were deposited on (0001) sapphire substrates by a reactive RF magnetron sputtering. The effect of post-annealing temperature on structural, optical, and electrical properties was investigated over the annealing temperatures from 400 to 800°C. The crystallinity of ZnO film grown at 600°C was significantly improved by annealing treatment while the film grown at 700°C showed little improvement with annealing. The near band edge emission peak of ZnO films grown at 600 and 700°C appeared at 3.26eV after thermal annealing, which was not observable in as-grown film. The ratio of near band edge emission intensity to deep level emission intensity increased with annealing temperatures below 700°C but thereafter decreased. The optical transmittance in the visible region was not influenced much by annealing treatment, showing around 85% for both as-grown and annealed films. The annealed ZnO films exhibited an n-type characteristics whereas high insulator characteristics were observed for as-grown samples. The superior carrier concentration, mobility, and resistivity were achieved with an annealing treatment. An optimum annealing treatment was found to be at 600°C. The ZnO film grown at 600°C followed by the optimum post annealing shows the most improved structural, optical, and electrical properties even better than those of the film grown at a higher growth temperature (700°C) with post-annealing. With Mg doping into ZnO film, blue shift of 150–200meV was observed, depending on the annealing temperature. The reactive RF magnetron sputtering coupled with an optimum annealing treatment would provide a promising and economically feasible method for optoelectronic device fabrication.

Effects of post-annealing temperature on structural, optical, and electrical properties of ZnO and Znl-xMgxO films by reactive RF magnetron sputtering

Effects of post-annealing temperature on structural, optical, and electrical properties of ZnO and Znl-xMgxO films by reactive RF magnetron sputtering

NEXAFS and X-ray scattering study of structure changes after post-annealing treatments of aligned MWNTs

The control of the crystallization degree is an important issue for carbon nanotube applications. In this context, we present the evolution of the structure after post-annealing treatment of multiwalled carbon nanotubes (MWNT), obtained by the aerosol pyrolysis process, involving liquid aerosols containing both hydrocarbon source and the metal catalyst precursor. The alignment and the degree of crystallinity of the raw and annealed carbon nanotubes have been quantified by X-ray diffraction measurements also used to analyze the metallic phases inside the nanotubes. The Near-Edge X-ray Absorption Fine Structure (NEXAFS) studies were performed at the C K-edge in order to follow the evolution of the electronic structure with the local structure and the degree of crystallinity of the nanotubes. We confirm that this chemical vapour deposition synthesis method enables to produce well-aligned multiwalled carbon nanotubes. The effect of post-annealing temperature both on local ordering and graphitization degree of nanotube walls are described. The results are compared to the previous observations of individual nanotubes by HRTEM concerning the structural changes occurring during annealing treatments.

Synthesis of (BiPb)2Sr2Ca2Cu3O10 superconducting thin films on MgO using a multilayered pulsed laser deposition method

Superconducting thin films of Pb-doped BiSrCaCuO have been prepared on (001) orientation MgO substrates by a multilayer pulse laser deposition technique using both BiPbSrCaCuO and PbO targets. The PbO target was used to dope Pb into the films in sufficient quantity to facilitate the growth of the 2223 phase. The effect of post-annealing temperature and time duration on the formation of this phase is described. Using x-ray diffraction and resistivity measurements we have found that a near optimum single phase 2223 film can be grown by post-annealing the sample at 854 °C for 15 h in air. The films grown are highly c-axis oriented and exhibit Tc(zero) as high as 105.5 K.