Tunable Microwave Device Fabrication on Low‐Temperature Crystallized Ba_0.5Sr_0.5TiO₃ Thin Films by an Alternating Deposition and Laser Annealing Process

Abstract

This article demonstrates a method to fabricate crystalline Ba0.5Sr0.5TiO3 (BST) thin films at a lower temperature of ≈300 °C using an excimer laser by an alternating depositing and annealing process. Firstly, a BST thin film with a thickness of ≈120 nm is deposited at 300 °C (laser energy of ≈2 J cm−2) and subsequently laser annealed (66 mJ cm−2) at 300 °C. This process is repeated five times to obtain thicker device quality films. XRD patterns, TEM, Raman, and UV–Vis–NIR spectroscopy confirm that phase formation of BST thin films has taken place. The band edge value for BST thin films is observed to decrease systematically from 4.65 eV (amorphous, 300 °C) to 3.56 eV (5‐layers, crystalline, 300 °C). A varactor device with a Circular Patch Capacitor (CPC) structure is patterned on the five‐stage laser annealed BST thin films processed at 300 °C, which shows a microwave tunability of 34% at 1 GHz compared to conventionally deposited BST films (prepared at 700 °C). This study provides a way for fabricating ferroelectric thin film based tunable devices at low temperatures, making the process compatible with low melting substrates in flexible electronics and other situations where there is a temperature constraint.

Photonic Drying/Annealing: Effect of Oven/Visible Light/Infrared Light/Flash-Lamp Drying/Annealing on WO3 for Electrochromic Smart Windows

“…28 The enhanced performance of visible-light-dried ECD may be due to the absorption band of WO 3 (band gap of 2.7 eV) in the visible region (WO 3 visible catalyst), which can absorb more light and improve its chemisorption of oxygen and evaporation of H 2 O molecules. 29,30 The improved chemisorbed oxygen improves the oxidation states of WO 3 and evaporation of water molecules, which results in higher optical modulation and long-life stability in ECDs.…”

Effect of Pulsed Laser Irradiation on Microstructure and Evolution of Residual Stress for Gold Film

“…When irradiating the material, laser energy is absorbed and the surface layer of the material is heated to a high temperature at a large heating rate, which are always accompanied by the origination of high stress and stress gradient. The high temperature together with the stress drive the material to evolve, like crystallinity improvement, [12][13][14] texture evolution, [15] voids elimination, [16] and recrystallization. [17] In the present study, according to the material analysis (Figure 2 and 3), the metastable as-deposited gold film recrystallized after laser irradiation.…”

“…[6,8] And this may bring about some detrimental changes, e.g., weakening the bonding between gold film and the substrate, and leading to grain boundary cracks. [8] Laser irradiation is a versatile mean in the machining and processing of materials [9][10][11] and was applied to regulate both the microstructure [12][13][14][15][16][17] and stress [17][18][19][20] of films and coatings. Goud [12] studied the laser irradiation of Ba 0.5 Sr 0.5 TiO 3 thin films, and the results showed that laser irradiation can turn the film deposited at low temperature from amorphous to crystalline.…”

“…[8] Laser irradiation is a versatile mean in the machining and processing of materials [9][10][11] and was applied to regulate both the microstructure [12][13][14][15][16][17] and stress [17][18][19][20] of films and coatings. Goud [12] studied the laser irradiation of Ba 0.5 Sr 0.5 TiO 3 thin films, and the results showed that laser irradiation can turn the film deposited at low temperature from amorphous to crystalline. Liu [13] studied the laser irradiation of CVD diamond coatings, and the results showed that the crystallinity improved significantly after laser irradiation.…”

Near‐Zero Thermal Expansion Ba1−xSrxZn2Si2O7‐Based Microwave Dielectric Ceramics for 3D Printed Dielectric Resonator Antenna with Integrative Lens

“…Owing to their high performance, microwave dielectric ceramics are usually treated as the main dielectric function materials in satellites, terminals, base stations, and other communication devices. [ 14–17 ] Microwave ceramic components, which has become a research hotspot worldwide, can better meet the demand for portability, miniaturization, and integration of communications equipment. [ 18,19 ] Near‐zero CTE ensures that DRAs operate within the variable temperature.…”