Effect of Postdeposition Annealing on the Structural, Electrical, and Optical Properties of DC Magnetron SputteredTa2O5Films

Abstract

Thin films of tantalum oxide were formed on quartz and silicon (111) substrates kept at room temperature (303 K) by reactive sputtering of tantalum target in the presence of mixture of oxygen and argon gases. The as-deposited films were annealed in air for an hour in the temperature range 673–873 K. The films were characterized by studying structural, dielectric, electrical, and optical properties. The as-deposited films were amorphous in nature. As the annealing temperature increased to 673 K, the films were transformed into polycrystalline. Electrical characteristics of as-deposited and annealedTa2O5thin films were compared. The thermal annealing reduced the leakage current density and increased the dielectric constant. The optical transmittance of the films increased with the increase of annealing temperature. The as-deposited films showed the optical band gap of 4.38 eV. It increased to 4.44 eV with the increase of annealing temperature to 873 K. The as-deposited films showed the low value (1.89) of refractive index and it increased to 2.15 when annealed at 873 K. The increase of refractive index with annealing temperature was due to the increase in the packing density and crystallinity of the films.

Pumping laser excited spins through MgO barriers

“…At distances more than 8μm away from the centre of the MTJ, the temperature remains largely unaffected. Considering the optical properties [21,23,24] This confirms the interface between the pillar stack and the Ta 2 O 5 as the only channel to transport the heat to the bottom CoFeB electrode, which because of the irregularities remaining form the patterning process leads to a reversal of the temperature gradient. Because the in-plane distance is one order of magnitude larger than the layer stack thickness, the temperature difference is low.…”

“…At distances more than 8μm away from the centre of the MTJ, the temperature remains largely unaffected. Considering the optical properties [21,23,24] of Ta 2 O 5 , our first interpretation of the sign change is that the heat is transported through the Ta 2 O 5 layer to the Ta bottom contact layer, which is distributed throughout the whole sample and as a result only the temperature of the bottom CoFeB layer increases. However, as stated in section 3.2, the laser power transmitted through the Au layer does not exceed 1%.…”