Optimized growth and dielectric properties of barium titanate thin films on polycrystalline Ni foils

Barium titanate(BTO) thin films were deposited on polycrystalline Ni foils by using the polymer assisted deposition(PAD) technique.The growth conditions including ambient and annealing temperatures were carefully optimized based on thermal dynamic analysis to control the oxidation processing and interdiffusion.Crystal structures,surface morphologies,and dielectric performance were examined and compared for BTO thin films annealed under different temperatures.Correlations between the fabrication conditions,microstructures,and dielectric properties were discussed.BTO thin films fabricated under the optimized conditions show good crystalline structure and promising dielectric properties with εr～ 400 and tan δ < 0.025 at 100 kHz.The data demonstrate that BTO films grown on polycrystalline Ni substrates by PAD are promising in device applications.     

柔性Pb(Zr_(0.53)Ti_(0.47))O_3薄膜的高温铁电特性

随着柔性电子产品的迅速发展,具有优异铁电和压电性的Pb(Zr_(0.53)Ti_(0.47))O_3 (PZT)薄膜在柔性的非易失性存储器、传感器和制动器等器件中有广泛的应用前景.同时,由于外部环境越来越复杂,具有高温稳定特性的材料和器件受到越来越多的关注.本文在耐高温的二维层状氟晶云母衬底上,用脉冲激光沉积技术制备出外延的PZT薄膜,并通过机械剥离的方法,得到柔性的外延PZT薄膜.研究了Pt/PZT/SRO异质结的铁电和压电性及其高温特性,发现样品表现出优越的铁电性,剩余极化强度(P_r)高达65μC/cm~2,在弯曲104次后其铁电性基本保持不变,且样品在275℃高温时仍然保持良好的铁电性.本文为柔性PZT薄膜在航空航天器件中的应用提供了实验基础.     

Structure and luminescence of a-plane GaN on r-plane sapphire substrate modified by Si implantation

We show the structural and optical properties of non-polar a-plane GaN epitaxial films modified by Si ion implantation. Upon gradually raising Si fluences from 5×10¹³ cm^-2 to 5×10¹⁵ cm^-2, the n-type dopant concentration gradually increases from 4.6×10¹⁸ cm^-2 to 4.5×10²⁰ cm^-2, while the generated vacancy density accordingly raises from 3.7×10¹³ cm^-2 to 3.8×10¹⁵ cm^-2. Moreover, despite that the implantation enhances structural disorder, the epitaxial structure of the implanted region is still well preserved which is confirmed by Rutherford backscattering channeling spectrometry measurements. The monotonical uniaxial lattice expansion along the a direction (out-of-plane direction) is observed as a function of fluences till 1×10¹⁵ cm^-2, which ceases at the overdose of 5×10¹⁵ cm^-2 due to the partial amorphization in the surface region. Upon raising irradiation dose, a yellow emission in the as-grown sample is gradually quenched, probably due to the irradiation-induced generation of non-radiative recombination centers.