材料科學(xué)與工程 材料物理與化學(xué)，外文文獻(xiàn)翻譯及原文

Surface effects on the piezoelectricity of ZnO nanowires

表面效應(yīng)對(duì)ZnO納米材料壓電性質(zhì)效應(yīng)的影響

a b s t r a c t
We utilize classical molecular dynamics to study surface effects on the piezoelectricproperties of ZnO nanowires as calculated under uniaxial loading. An important point toour work is that we have utilized two types of surface treatments, those of chargecompensation and surface passivation, to eliminate the polarization divergence thatotherwise occurs due to the polar (0001) surfaces of ZnO. In doing so, we find that ifappropriate surface treatments are utilized, the elastic modulus and the piezoelectricproperties for ZnO nanowires having a variety of axial and surface orientations are allreduced as compared to the bulk value as a result of polarization reduction in the polar[0001] direction. The reduction in effective piezoelectric constant is found to beindependent of the expansion or contraction of the polar (0001) surface in responseto surface stresses. Instead, the surface polarization and thus effective piezoelectricconstant is substantially reduced due to a reduction in the bond length of the Zn–Odimer closest to the polar (0001) surface. Furthermore, depending on the nanowireaxial orientation, we find in the absence of surface treatment that the piezoelectricproperties of ZnO are either effectively lost due to unphysical transformations from thewurtzite to non-piezoelectric d-BCT phases, or also become smaller with decreasingnanowire size. The overall implication of this study is that if enhancement of thepiezoelectric properties of ZnO is desired, then continued miniaturization of square ornearly square cross-section ZnO wires to the nanometer scale is not likely to achievethis result.

摘要：?jiǎn)屋S晶體的計(jì)算中，我們使用經(jīng)典分子動(dòng)力學(xué)理論去研究表面效應(yīng)對(duì)ZnO納米材料壓電效應(yīng)的影響。我們工作的一個(gè)重點(diǎn)是我們使用兩種表面處理方式，這些處理方式為了排除ZnO極性面（0001）導(dǎo)致的極化分歧，改變了補(bǔ)償和表面鈍化。做了這些處理后，我們發(fā)現(xiàn)如果利用適當(dāng)?shù)谋砻嫣幚恚琙nO的的彈性模量和壓電性質(zhì)有各種的軸向，并且相對(duì)于大多數(shù)由于（0001）極化面的極化削減表面極化都進(jìn)一步減少了。有效壓電常數(shù)的減少被發(fā)現(xiàn)是基于極化面（0001）表面響應(yīng)膨脹或收縮帶來(lái)的表面壓力。相反，表面極化和有效壓電常數(shù)大幅度減少是由于Zn–O二聚體的鍵長(zhǎng)接近極性面（0001）表面。再者，根據(jù)納米線軸向的極化，我們發(fā)現(xiàn)經(jīng)過(guò)表面處理后ZnO的壓電效應(yīng)由于從纖維鋅礦相轉(zhuǎn)變非壓電d-BDT相的非物質(zhì)轉(zhuǎn)變明顯的損失，并且也隨著納米線大小的增長(zhǎng)而減小。這個(gè)研究整體的意義就在于如果增強(qiáng)ZnO對(duì)壓電性能的要求，然后再繼續(xù)小型化的平方或近方形截面的ZnO納米線是不可能獲得這個(gè)結(jié)果的。