The crystallization kinetics of the pyrochlore to perovskite phase transformation in lead zirconate titanate (PZT) thin films have been analyzed using rapid thermal processing (RTP). Sol-gel PZT thin films, fabricated on platinum electrodes, were annealed at 550 °C to 650 °C with hold times ranging from 1 s to 5 min. Glancing angle x-ray diffraction (XRD) was used for depth profiling to identify the location of phases in the films. Transmission electron microscopy (TEM) provided information on grain structure, nucleation, and growth. The phase information was correlated to the ferroelectric and dielectric properties. The perovskite phase nucleated in the pyrochlore phase throughout the film thickness, and at 650 °C the transformation was complete in 15 s. Fast growing (100) PZT nucleated at the platinum and consumed a small-grained matrix until a columnar structure was obtained. A ramp rate of 100 °C/s was sufficiently fast to prevent transformation during heating and allowed the direct application of an Avrami model for transformation kinetics. An activation energy of 610 kJ/mol was determined.

Measurements of the attenuation and velocity of pulsed high-frequency sound have been performed up to 133 MHz in superfluid 3 He-Z?. A new collective mode of the order parameter was discovered at a frequency extrapolated to T c of oo = (1.165 ± 0.05)A K:s (T c ), where ABC S (T) is the energy gap in the weak-coupling BCS theory. The group velocity has been observed to decrease by as much as | of the zero-sound velocity.

Two-dimensional carrier profiling using scanning spreading resistance microscopy (SSRM) has recently been reported for Si- and InP-based structures. In this article, we report SSRM measurements solely on III–V material-based structures. We have studied GaAs and InP doping staircase structures, prepared using molecular-beam epitaxy. These structures were then used as calibration standards for the profiling of carrier density in state-of-the-art III–V-based optoelectronic devices. We discovered that SSRM data on GaAs can be obtained with either polarity; however, only one polarity (positive or negative sample bias for n- or p-GaAs, respectively) produces SSRM results that show quantitative correlation with dopant concentration as determined by secondary ion mass spectrometry (SIMS). In comparison, SSRM measurements using both bias polarities on n-InP correlates well with SIMS, while p-InP exhibits a similar polarity dependence to p-type GaAs. A physical model based on a Schottky junction is proposed to explain these results. We also report calibrated SSRM measurements on GaAs and InP heterojunction bipolar transistor structures.

Articles you may be interested inDemonstration of transverse-magnetic deep-ultraviolet stimulated emission from AlGaN multiple-quantum-well lasers grown on a sapphire substrate Appl. Phys. Lett. 106, 041115 (2015); 10.1063/1.4906590 Two-dimensional profiling of carriers in a buried heterostructure multi-quantum-well laser: Calibrated scanning spreading resistance microscopy and scanning capacitance microscopy Reliability and low-frequency noise measurements of InGaAsP multiple quantum well buried-heterostructure lasers J.Differential gain and threshold current of 1.3 μm tensile-strained InGaAsP multi quantum well buriedheterostructure lasers grown by metalorganic molecular beam epitaxial growthWe report results of two-dimensional local potential measurement of the transverse cross-section of operating buried-heterostructure ͑BH͒ multiple-quantum-well lasers. The measured two-dimensional image of potential distribution resolved clearly the multiquantum-well active region and the p-n-p-n current-blocking structure of the BH laser, showing close correlation to the scanning spreading resistance microscopy image. Nanopotentiometry measurements were also performed on the p-n-p-n current-blocking structure of a BH laser under different forward bias voltages. The nanopotentiometry results provide direct insight into the behavior of p-n-p-n current-blocking layers intended to minimize current leakage. Our results demonstrate the application of nanopotentiometry to the delineation of complex buried structures in quantum optoelectronic devices.

Two-dimensional (2D) carrier concentration profiling using scanning spreading resistance microscopy (SSRM) has been carried out on molecular beam epitaxy-grown GaAs and InP dopant calibration samples. The current transport mechanisms between the diamond-coated SSRM tip and the III–V semiconductor cleaved surface (110) was investigated as a function of semiconductor dopant concentration via current–voltage (I–V) measurement. A positive or negative tip bias was applied while scanning over each dopant concentration region (1016–1019 cm−3). The results were compared to simulated I–V curves based on thermionic emission theory. The best fits to the data obtained under forward bias indicated that the contact barrier heights, φb, were much lower than expected from conventional large area planar contacts to GaAs or InP. The effect increases with increasing doping concentration, as a result of a combination of barrier height lowering mechanisms such as image forces, thermionic field emission and minority carrier injection. Under reverse bias, the thermionic emission theory only holds for highly doped semiconductors while for low doping, surface and bulk generation currents determine the overall detectable SSRM current.