Enhancement of crystal anisotropy and ferroelectricity by decreasing thickness in (Al,Sc)N films
Enhancement of crystal anisotropy and ferroelectricity by decreasing thickness in (Al,Sc)N films
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DOI：
10.2109/jcersj2.21184
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发表时间：
2022-07
影响因子：
1.1
通讯作者：
Shinnosuke Yasuoka;R. Mizutani;Reika Ota;T. Shiraishi;Takao Shimizu;S. Yasui;Yoshitaka Ehara;K. Nishida;M. Uehara;Hiroshi Yamada;M. Akiyama;Y. Imai;O. Sakata;H. Funakubo
中科院分区：
文献类型：
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作者：
Shinnosuke Yasuoka;R. Mizutani;Reika Ota;T. Shiraishi;Takao Shimizu;S. Yasui;Yoshitaka Ehara;K. Nishida;M. Uehara;Hiroshi Yamada;M. Akiyama;Y. Imai;O. Sakata;H. Funakubo
研究了在（111）Pt / TiO x / sio2 / (100)Si衬底上沉积厚度为12 ~ 130 nm的（Al 0.8 Sc 0.2）N薄膜的晶体结构和铁电性能与厚度的关系。表征纤锌矿结构晶体各向异性的内部结构参数u随着薄膜厚度的减小而减小。这主要是由于（Al 0.8 Sc 0.2）N膜的原子距离比Pt层大，从而产生了面内压缩应变。在室温下，厚度为20nm的薄膜获得了饱和的P r值。当测量温度升高到150℃时，12nm厚薄膜的P r值在电场作用下趋于饱和。在20nm以下的厚度区域，这些P r值明显高于传统铁电材料，如Pb(Zr,Ti) o3和HfO 2基薄膜。当膜厚小于50 nm时，P r值有增大的趋势。这是由于由于Pt层的应变，晶体各向异性随着薄膜厚度的减小而增加。此外，这些应变薄膜的显著P r值大于纯AlN的期望值，并且与基于晶体各向异性u参数的理论计算预测相吻合。这说明（Al,Sc）N的P r值主要由u参数控制。
The thickness dependences of crystal structures and ferroelectric properties were investigated for (Al 0.8 Sc 0.2 )N fi lms with thicknesses of 12 to 130 nm deposited on (111)Pt / TiO x / SiO 2 / (100)Si substrates. The internal structural parameter u , representing the crystal anisotropy of the wurtzite structure, decreased with decreasing fi lm thickness. This was attributable mainly to the in-plane compressive strain originating from the larger atomic distance of (Al 0.8 Sc 0.2 )N fi lm compared to that of the underlying Pt layer. Well-saturated P r values were obtained at room temperature for the fi lms down to 20 nm in thickness. The P r value of the 12-nm-thick fi lm tended to saturate against the electric fi eld when the measurement temperature increased to 150 °C. These P r values are considerably higher than those of conventional ferroelectric materials such as Pb(Zr,Ti)O 3 and HfO 2 -based fi lms in the thickness region below 20 nm. The P r value tended to increase for fi lm thicknesses below 50 nm. This originated from the increase in crystal anisotropy with decreasing fi lm thickness due to the strain from the underlying Pt layers. Moreover, the signi fi cantly large P r values of these strained fi lms were larger than the expected values of pure AlN and were in good agreement with the theoretically calculated predictions based on the crystal anisotropy, u parameter. This suggests that the P r values of (Al,Sc)N can be controlled mainly by the u parameter.