Jinn P. Chu

Growth-Temperature-Dependent Electrical Properties of Mn Doping Ba0.5Sr0.5TiO3 Thin Films on La0.72Ca0.28MnO3 Electrodes

Ba0.5Sr0.5TiO3 (BST) thin films doped with 3 mol % Mn were fabricated on La0.72Ca0.28MnO3-coated SrTiO3(001) substrates. The effects of growth temperature and Mn doping on the lattice and electrical properties of the BST films were studied. Mn-doped BST films have rougher surfaces and larger grains than undoped BST films. Adding Mn dopants to BST films improves their dielectric constant, tunability, and leakage-current characteristics. Additionally, the degree of improvement of the electrical characteristics of the Mn-doped BST film depends strongly on the growth temperature. The higher growth temperature of the Mn-doped BST film is associated with a greater improvement in the dielectric constant and a more favorable figure of merit than in the undoped case. The tunability of the Mn-doped BST film that was deposited at 750 °C was enhanced from 41 to 60%; the figure of merit increased from 13 to 53, and the leakage current density was approximately one order of magnitude lower than that of the undoped film at an applied electric field of 300 kV/cm. The results demonstrate that Mn-doped BST films with appropriately controlled growth temperatures have potential for use in tunable devices.

Sn whisker mitigation by a thin metallic-glass underlayer in Cu-Sn

This study investigates the effects of thin film metallic glass (TFMG) as an underlayer on the Sn whisker mitigation in the Cu-Sn couples. Samples with and without TFMG underlayers were subjected to various heat treatments at elevated temperatures up to 85 °C in monotonic and cyclic modes. TFMG underlayer effectively blocks the Cu/Sn interaction even with the thickness as thin as 25 nm. In addition, with very thin thickness, the introduction of TFMG underlayer is expected to yield insignificant degrees of compressive stress, which is anticipated to occur when the samples are exposed to thermal cycling. Their thin thickness and amorphous nature are considered beneficial to make TFMGs as a promising diffusion barrier for Sn whisker mitigation.

Imprinting of Metallic Glasses: A Simple Approach to Making Durable Terahertz High-Pass Filters

An imprint process of Pd-based metallic glass is used to create a high-aspect-ratio two-dimensional wire array structure for filtering terahertz (THz) radiation. By the simplified imprinting process, a 10×10 straight wire array with a wire height of ~320 µm and a diameter of 100.6 µm is produced. The negligibly small expansion of ~0.3% confirms the excellent thermal imprinting property of metallic glass. The periodic wire array is shown to act as a high-pass filter in the THz range, and the transmission property measurement reveals a turn-on frequency of 0.4 THz, suggesting the promising approach and material for robust high-pass filters.

Fracture-resistant thin-film metallic glass: Ultra-high plasticity at room temperature

We report the first example of room-temperature rubber-like deformation in thin-film metallic glasses (TFMGs), 260-nm-thick Zr60Cu24Al11Ni5 layers, under ultra-high shear strain. The TFMGs were deposited, with no external heating, on Zr-based bulk metallic glass (BMG) and Si(001) substrates by rf magnetron sputtering in a 3 mTorr Ar plasma. Cross-sectional transmission electron microscopy (XTEM) analyses and nanoindentation results reveal that the TFMGs undergo an incredibly large shear strain, estimated to be ∼4000%, during fatigue tests, and thickness reductions of up to 61.5%, with no shear-banding or cracking, during extreme nanoindentation experiments extending through the film and into the substrate. TFMG/BMG samples also exhibit film/substrate diffusion bonding during deformation as shown by high-resolution XTEM.

Thin film metallic glass as a diffusion barrier for copper indium gallium selenide solar cell on stainless steel substrate: A feasibility study

The feasibility of using Zr53.5Cu29.1Al6.5Ni10.9 thin-film metallic glass (TFMG) as a diffusion barrier for copper indium gallium selenide (CIGS) solar cells on stainless steel (SS) is investigated. The detrimental Fe diffusion from SS into CIGS is found to be effectively hindered by the introduction of a 70-nm-thick TFMG barrier; the cell performance is thus improved. Compared with the 2.73% of CIGS on bare SS, a higher efficiency of 5.25% is obtained for the cell with the Zr52Cu32Al9Ni7 TFMG barrier.

Few Layers Thin Film Metallic Glass Enhanced Optical Properties of ZnO Nanostructures

A few layers of Cu-based (Cu47Zr42Al7Ti4) thin-film metallic glasses (TFMGs) were sputtered on hydrothermally synthesized ZnO nanowires/glass and ZnO nanotubes/glass to fabricate UV photodetectors. The few layers of Cu-based TFMG are ultrathin at ∼0.98 nm and have a noncrystalline metal structure according to X-ray diffraction, Raman, photoluminescence, and high-temperature transmission electron microscopy verification. The photoresponse performance of the coated few-layers Cu-TFMG samples was enhanced 1680-7700% compared with the noncoated sample. The few-layers Cu-TFMG has high transmittance ∼90% in the visible band and creates a large capacitor to absorb UV photocurrent and release dark current.