W. L. Zhang

Great enhancement of pyroelectric properties for Ba0.65Sr0.35TiO3 films on Pt–Si substrates by inserting a self-buffered layer

(100)-Ba0.65Sr0.35TiO3 (BST) films were deposited on Pt/Ti/SiO2/Si substrates using a low-temperature self-buffered layer. X-ray diffraction and atomic force microscope investigations show that the microstructure of BST films strongly depends on surface morphology of annealed self-buffered layer. The mechanism of nucleus formation and the growth initiation of BST films on self-buffered layers were proposed. It was found that the pyroelectric properties of BST films can be greatly enhanced. The pyroelectric coefficient and material merit figure of (100)-BST films are 1.16×104u2002μCu2009m−2u2009K−1 and 2.18×10−4u2002Pa−1/2, respectively. The detectivity of 9.4×107u2002cmu2009Hz1/2u2009W−1 was obtained in the (100)-BST film capacitors thermally isolated by 500 nm SiO2 films.

The structure and soft magnetic properties of rapid recurrent thermal annealing CoNbZr nanocrystalline alloys thin films

Abstract Soft magnetic thin film and devices, especially nanometer crystal soft magnetic thin film, are touching in peoples attention with good quality and widely application. We have developed a new method to use to nanocrystallize the amorphous CoNbZr thin film fabricated by DC magnetic sputtering under different conditions. The grain size of this film can be fined to 20–30 nm, the structure and properties of nanometer crystal thin film obviously be improved as controlling the temperature duration and recurrent times. The permeability increase from 3500 to over 5000, coercivity decrease from 4.6 to 1.5 Oe, resistivity from 1.4 to 0.5 Ωcm. The great improvement of soft magnetic film properties has obtained.

Effects of SrTiO3/TiO2 buffer layer on structural and electrical properties of BiFeO3 thin films grown on GaN (0002)

BiFeO3(BFO) films were deposited by pulsed laser deposition on GaN(0002)/c-sapphire. X-ray diffraction data show that BFO(111) epitaxial films was deposited on SrTiO3/TiO2 double-layer buffered GaN, compared to the polycrystalline film grown directly on GaN. The epitaxial relationships of BFO film with SrTiO3/TiO2 buffer layers were BFO [11-2](111)//GaN [1-100](0002) as revealed by XRD phi scans. Furthermore, BFO films on SrTiO3/TiO2 buffer exhibited enhanced electric properties compared to these deposited directly on GaN. The remnant polarization was improved about 30% while the leakage current was reduced by nearly three orders of magnitude. The epitaxial growth promoted by the SrTiO3/TiO2 buffer layer is a pivotal parameter in the improved electric properties of BFO films on GaN (0002).

Enhanced pyroelectric property of PMN–PT/P[VDF–TrFE] thick film by optimizing poling temperature

Lead magnesium niobate–lead titanate (PMN–PT) ceramic powder and Poly[VinyliDeneFluoride-co-TriFluoroEthylene] (P[VDF–TrFE]) have been used to fabricate 0–3 composites thick films on ITO substrates by tape casting. The phase structure and grain size of PMN–PT were analyzed by XRD and SEM. The distribution of ceramic powder in polymer matrix was characterized by SEM. In order to find out the optimal poling temperature, dielectric-temperature spectrums of the composite films were measured to calculate the electric field applied to the ceramic phase (Ec). Finally, PMN–PT/P[VDF–TrFE] composite films were polarized by one-step polarization under optimized polarization temperature and their pyroelectric constant were compared with these of samples poled using conventional two-step polarization method. The results showed that the pyroelectric coefficient increases to 58.6xa0μCxa0m−2xa0K−1 at a ceramic mass fraction of 55% at the optimized polarizing temperature 110u2009°C.

Pb(ZrTi)0.98Mn0.02O3 weight ratio effects on the properties of Pb(ZrTi)0.98Mn0.02O3/P(VDF-TrFE) composite film and infrared detectors

The effect of Pb(ZrTi)0.98Mn0.02O3 (PZTM) weight ratio on the properties of PZTM/P(VDF-TrFE) pyroelectric composites and devices was reported in this paper. Infrared devices were fabricated using PZTM/P(VDF-TrFE) composite films with different weight ratio. The pyroelectric coefficient, the dielectric properties and the infrared absorptivity of the composite materials have been measured. It was found that the pyroelectric constant of the composite decreased as PZTM weight increased. In contrast, the dielectric permittivity increased as PZTM weight increased. Especially, the composite with 0.41 PZTM weight ratio showed the smallest dielectric loss and largest infrared absorptivity. The properties of the detectors fabricated using the composite materials with different PZTM weight ratio have been further tested. It was found that the infrared irradiation absorptivity showed great impact on the performance of the devices other than the pyroelectric coefficient and dielectric permittivity.

Effects of the TiO2 buffer thickness on SrTiO3 (111) epitaxial films grown on GaN (0002)

SrTiO3 (STO) films have been grown on TiO2-buffered GaN(0002) substrates. The deposition process was in situ monitored by reflective high energy electron diffraction (RHEED). The deposition rate and in-plane lattice parameter of TiO2 were calculated from the oscillation curve and RHEED patterns, respectively. It was found that the TiO2 lattice parameter changed as the thickness increased, which indicated a strain relaxation process of TiO2 buffer layers during the deposition. We show that the thickness of TiO2 can significantly influence the STO growth mode, surface morphology, and crystalline quality. As the TiO2 thickness increased, the STO growth mode is changed from 3D island to 2D growth mode and finally to SK mode as revealed by RHEED. The growth mode evolution shows close relation with the surface morphology and crystalline quality of STO. STO films deposited on 2u2009nm thick TiO2 film show 2D growth mode and have smoothest surface and smallest full width at half maximum of the STO rocking curve. Our ...

Stress dependence of magnetic domains in FeCoSiB amorphous films

The work reports the effect of a tensile stress on the magnetic domain of FeCoSiB amorphous films. The domain structures of the unstressed and stressed FeCoSiB amorphous films with different tensile strains have been studied by magnetic force microscopy (MFM). With the increase of the tensile stress in the samples, it has been observed that the domain structures transform from irregular domains into parallel strip domains, and magnetic contrasts decrease. The MFM image disappears when the tensile stress is strong enough. A model has been presented to explain the evolution of the domain structures under the tensile stress. The effects of the stress on the domain of the films have been discussed.

Magnetoresistance and performance of amorphous-CoNbZr∕Co∕Cu∕Co magnetic multilayers

A pseudo spin-valve (PSV) using amorphous CoNbZr alloy as a soft magnetic layer and buffer layer was proposed. The giant magnetoresistance (GMR), thermal annealing effect, and the performance were investigated. Antiparallel magnetization alignments were observed in the samples with 2–4nm CoNbZr layer and a maximum GMR of 6.5% was obtained. Furthermore, sandwich with relatively thick CoNbZr layer has a superior thermal stability to 400°C and a GMR enhancement to about 9%. After patterning to 6μm×1μm elliptic stripe, a single domain forms and the dynamic MR behavior indicates the stripe has a linear and stable GMR response. Therefore, it is believed that the PSVs with amorphous CoNbZr layers have good potentials for spin-electronic devices.