ZnOTe Compounds Grown by DC-Magnetron Co-Sputtering

ZnOTe compounds were grown by DC magnetron cosputtering from pure Tellurium (Te) and Zinc (Zn) cathodes in O2/Ar atmosphere. The applied power on the Zn target was constant equal to 100 W, while the one applied on the Te target took two values, i.e., 5 W and 10 W. Thus, two sample series were obtained in which the variable parameter was the distance from the Te targets to the substrate. Sample compositions were determined by Rutherford Backscattering Spectroscopy (RBS) experiments. Structural analysis was done using X-Ray diffraction (XRD) spectrometry and the growth of the hexagonal w-ZnO phase was identified in the XRD spectra. RBS results showed high bulk homogeneity of the samples forming ZnOTe alloys, with variable Te molar fraction (MF) ranging from 0.48–0.6% and from 1.9–3.1% for the sample series obtained at 5 W and 10 W, respectively. The results reflect great differences between the two sample series, particularly from the structural and optical point of view. These experiments point to the possibility of Te doping ZnO with the permanence of intrinsic defects, as well as the possibility of the formation of other Te solid phases when its content increases. The results and appreciable variations in the band gap transitions were detected from Photoluminescence (PL) measurements.

The Use of Dewpoint Hygrometry to Measure Low Water Potentials in Soilless Substrate Components and Composites

Plant water availability in soilless substrates is an important management consideration to maximize water efficiency for containerized crops. Changes in the characteristics (i.e., shrink) of these substrates at low water potential (<−1.0 MPa) when using a conventional pressure plate-base can reduce hydraulic connectivity between the plate and the substrate sample resulting in inaccurate measures of water retention. Soilless substrate components Sphagnum peatmoss, coconut coir, aged pine bark, shredded pine wood, pine wood chips, and two substrate composites were tested to determine the range of volumetric water content (VWC) of surface-bound water at water potentials between −1.0 to −2.0 MPa. Substrate water potentials were measured utilizing dewpoint hygrometry. The VWC for all components or composites was between 5% and 14%. These results were considerably lower compared to previous research (25% to 35% VWC) utilizing conventional pressure plate extraction techniques. This suggests that pressure plate measurements may overestimate this surface-bound water which is generally considered unavailable for plant uptake. This would result in underestimating available water by as much as 50%.

Substrate Temperature Effect on the Spectrum Emission in Superconductor Heterostructure BiPbSrCaCuZnO

This paper shows the applied voltage effect on the superconductor substrate sample. The substrate temperature (Ts) increases the activation energy of the substrate atoms. Thus, the injecting of minority carriers (holes) increased in ZnO semiconductor. These carriers recombine with electrons of 4S1 shell for Cu atom. The recombination occurs by two ways from band to band (direct recombination) or via traps (indirect recombination). The recombination mechanisms produce photons emission in the ultraviolet and visible spectrum. The calibration between voltage and temperature achieved using Variac device. The applied voltages were 60, 65, 70, and 80 Volt, and the recorded substrate temperatures were 300, 320, 350, and 400 °C, respectively.

Nonwetting Effects of Si Contamination on Cu Bumps of a Flip Chip Package—A Case Study

Presence of foreign materials (i.e, contamination) can affect the reliability of copper (Cu) bumps when it affects the wettability of the solder and consequently weakens the joint formation of the copper to the substrate. This paper looks at a case of non-wetting of Cu bumps due to silicon contamination induced during assembly processing. In this case study, surface roughness is the main factor being altered when foreign materials contaminate the metal substrate. Sample devices were tested in a resistive open unit and a direct current failing unit, respectively. It was found that the silicon dust present on the substrate in effect "roughens" the surface, thereby decreasing the wettability between the molten solder to the metal substrate. For future studies, it is recommended that the effect of reliability stress activities on the Cu bumps with silicon contaminations be examined to evaluate the risks for possible field failures of this defect.

Determination of Relationship between Chemical Composition of Electrolyte and Surface Sample Quality

Paper tracks experimentally confirmed relationship between chemical composition of electrolyte and resulting surface finish quality of created oxide layer during the process of anodic oxidation of aluminium. Examined chemical factors were: concentrations of sulphuric acid, oxalic acid, boric acid and sodium chloride. Aggressive effects of electrolyte were chosen as indicator of resulting layer quality – presence and extent of etching of used substrate sample.

Impact of Surface Roughness on Formation of Micro Cracks and Fatigue Performance

Tungsten-doped diamond-like carbon (DLC) coatings have been magnetron sputtered with chromium and chromium/tungsten carbide dual interlayers onto 410 stainless steel rods. The surface finish (Ra) of the substrate before deposition was 0.10–0.25 μm for a set of rough rods and 0.05 to 0.10 μm for a set of smooth rods. SEM analyses revealed different kinds of flaws in the as-deposited films (virgin coating). Two samples, one from each set, were fatigue tested under uni-axial tension to determine the effect of the substrate surface roughness on the performance of the coating. Surface analysis revealed a different response between films deposited on rough and smooth substrates. Severe failure modes such as spalling and wide cracks developed from initial film flaws in the rough substrate sample. Cracks and film spalling were also observed in the smooth substrate sample but the severity, in terms of crack dimensions and density was considerably lower than the rough substrate sample.

SPIN-RESOLVED PHOTOELECTRON SPECTROSCOPY OF ULTRATHIN Fe FILMS ON GaAs(001)

Thin epitaxial Fe films were grown on singular and vicinal GaAs(001) substrates, and their magnetic and electronic structures were investigated by synchrotron-based spin-resolved and spin-integrated photoelectron spectroscopy with different Fe thickness. There were two types of substrates: one was a Si-doped n-type GaAs(001) surface with doping concentration of 2 × 1018 cm -3 (singular substrate), and the other was orientated by 3° toward the (111)A direction (vicinal substrate). Spin polarization of the secondary electron peak at different growth stages of Fe coverage for the singular substrate sample and the vicinal one were measured. In the case of singular substrates, there was a dependence of their initial surface reconstruction, which is associated with complex domain structure, while no such the dependence was observed in the case of vicinal substrates. The result from the vicinal sample suggests the geometrical influence of the initial surface stoichiometry of the substrate.