Cao Li-Xin

Structural and Electrical Characteristics of Pb(Zr 0.53 ,Ti 0.47 )O 3 Thin Films Deposited on Si (100) Substrates

Pb(Zr0.53, Ti0.47)O3 (PZT) films were directly deposited on Si substrates without a buffer layer by pulsed laser deposition. Only (110)-oriented PZT peaks (other than Si substrate peaks) were observed from the XRD data. The electrical properties of the PZT/Si capacitor were characterized in terms of both the capacitance versus voltage (C–V) and current versus voltage (I–V) measurements. The clockwise trace of the C–V curve shows ferroelectric polarization switching, as is expected. From the I–V curves, the Schottky emission and space-charge-limited-current behaviour are found to be the mainly leakage current mechanism in a certain electric field range in the negative and positive bias, respectively.

Structural and Electrical Properties of Barium Strontium Titanate Thin Film on Conductive La1−xSrxMnO3 Bottom Layer

Ferroelectrics and colossal magnetoresistance heterostructure Ba1−xSrxTiO3(BST)/La1−xSrxMnO3 (LSMO) have been fabricated on a LaAlO3 substrate by the pulse laser deposition method. The dielectric measurements show that at room temperature and 100 kHz, the dielectric constant and loss tangent are about 990 and 0.012, respectively; the highest tunability is about 45% near 200 K under the applied electric field of 200 kV/cm. Further study indicates that the leakage current for the BST/LSMO heterostructure obeys the Schottky emission mechanism in the electric field region higher than 100 kV/cm at room temperature.

A New Bipolar Type Transistor Created Based on Interface Effects of Integrated All Perovskite Oxides

Oxide transistor is the basic device to construct the oxide electronic circuit that is the backing to develop integrated oxide electronics with high efficiency and low power consumption. By growing the perovskite oxide integrated layers and tailoring them to lead semiconducting functions at their interfaces, the development of oxide transistors may be able to perform. We realize a kind of p-i-n type integrated layers consisting of an n-type cuprate superconductor, p-type colossal magnetoresistance manganite, and a ferroelectric barrier (i). From this, bipolar transistors were fabricated at the back-to-back p-i-n junctions, for which the Schottky emission and p-n junction barriers, as well as the ferroelectric polarization, were integrated into the interfaces to control the transport properties; a preliminary but distinct current gain greater than 1.6 at input current of microampers order was observed. These results present a real possibility to date for developing bipolar all perovskite oxide transistors.

Sensitive detection of infrared photons using a high-Q microcantilever

A new approach based on microcantilevers is presented to detect infrared photons with high sensitivity. Infrared photons are measured by monitoring the amplitude change of a vibrating microcantilever under light pres- sure force. The irradiating light is modulated into sinusoidal and pulsed waves, and to be in-phase and anti-phase with the cantilever driving signal. A linear relationship between the amplitude change of the cantilever and the light power distributing on the cantilever was observed. Under a vacuum of 10 4 Pa, an infrared light power of 7.4 nW was detected with the cantilever. The in-phase and anti-phase modulation to the cantilever vibration using a pulsed light results in an enhanced response of the cantilever.

The electric and magnetic properties of epitaxially grown A0.5−xLaxSr0.5MnO3 (A=Pr, Nd) thin film

The epitaxial (single crystal-like) Pr0.4La0.1Sr0.5MnO3 (PLSMO) and Nd0.35La0.15Sr0.5MnO3 (NLSMO) thin films are prepared and characterized, and the electric and magnetic properties are examined. We find that both PLSMO and NLSMO have their own optimum deposition temperature (To) in their growing into epitaxial thin films. When the deposition temperature is higher than To, a c-axis oriented but polycrystalline thin film grows; when the deposition temperature is lower than To, the thin film tends to be a-axis oriented and also polycrystalline. The most important point is that for the epitaxial PLSMO and NLSMO thin films the electronic phase transitions are closely consistent with the magnetic phase transitions, i.e. an antiferromagnetic phase corresponds to an insulating state, a ferromagnetic phase corresponds to a metallic state and a paramagnetic phase corresponds to a semiconducting state, while for the polycrystalline thin films the electronic phase transitions are always not consistent with the magnetic transitions.

Full aging in spin glass state of Y0.90Na0.10MnO3

We study the decays of the thermoremanent magnetization in Y0.90Na0.10MnO3 for different waiting times at the measuring temperature 33 K, well below the spin glass (SG) transition temperature 42 K. The results demonstrate that almost perfect full aging can appear even in the case of the cooling time as long as 700 s from 60 K to 33 K. By subtracting the stationary component A(τ0/t)a (A is a dimensionless constant, t represents the time, τ0 is the microscopic spin flipping time, and α is a parameter always in the rang of 0.1–0.01), the value of α is found to be much smaller than that reported in other SG systems, which is well consistent with the behaviour of the ac susceptibility. All of them are discussed based on the intrinsic geometric magnetic frustration for the present system.