负偏置沉积法可控制备CuO多孔纳米结构薄膜

由于具有低成本、无毒、铜源丰富等优点,以及在气敏传感器、太阳能电池、光催化等领域的潜在应用前景,CuO薄膜引起了人们的广泛关注.采用射频平衡磁控溅射镀膜系统,在薄膜沉积过程中通过施加不同衬底负偏压可控制备了CuO多孔纳米结构薄膜.研究发现,所得CuO薄膜具有灵活可调的孔隙度和纳米构筑单元形貌特征,并且它们与衬底负偏压的大小密切相关;薄膜沿衬底法线方向呈柱状生长且具有显著的（111）择优取向;禁带宽度在2.0.35 eV之间可调.很明显地,传统的溅射离子轰击、再溅射理论并不适合用来解释上述负偏压效应,因此在此基础上提出了一种负偏置沉积过程中材料原子或分子在薄膜表面选择性优先沉积机制.国家自然科学基金(51501018,11574255)；江苏省自然科学基金(BK20150267,BK20141169)；江西省教育厅科技项目(GJJ161197)；江西省自然科学基金(20132BAB212005)资助

Controllable fabrication of Cu_2O porous nanostructured films by negative bias deposition method

由于具有低成本、无毒、铜源丰富等优点,以及在气敏传感器、太阳能电池、光催化等领域的潜在应用前景,; Cu_2O薄膜引起了人们的广泛关注.采用射频平衡磁控溅射镀膜系统,在薄膜沉积过程中通过施加不同衬底负偏压可控制备了Cu_2O多孔纳米结构薄膜.研; 究发现,所得Cu_2O薄膜具有灵活可调的孔隙度和纳米构筑单元形貌特征,并且它们与衬底负偏压的大小密切相关;薄膜沿衬底法线方向呈柱状生长且具有显著; 的(111)择优取向;禁带宽度在2.0~2.35; eV之间可调.很明显地,传统的溅射离子轰击、再溅射理论并不适合用来解释上述负偏压效应,因此在此基础上提出了一种负偏置沉积过程中材料原子或分子在薄; 膜表面选择性优先沉积机制.As one of the most common two kinds of copper oxides, cuprous oxide; (Cu_2O) is an important p-type transition metal oxide semiconductor; material. Due to the advantages of low-cost, non-toxicity and abundant; copper sources and the potential applications in the fields of gas; sensors, solar cells and photocatalysts, thin films of Cu_2O have; attracted great interest of researchers. To enhance the performances of; the above Cu_2O-based surface-sensitive devices and materials, the; researchers tend to prepare Cu_2O thin films of porous or even; nanoporous structures. However, there is still no effective method; available for the controllable fabrication of Cu_2O porous; nanostructured films (or porous nanostructure-films, short for PNFs),; which owns not only the common features of porous thin films but also; the unique properties of nanosize building units. By using a; radiofrequency balanced magnetron sputtering (MS) deposition system, in; this paper, Cu_2O PNFs were prepared on clean glass slides by applying; different negative bias voltage during film deposition. After the; preparation, a field-emission scanning electron microscope (FESEM), a; grazing-incidence X-ray diffractometer (GIXRD) and an; ultraviolet-visible (UV-Vis) spectrophotometer were applied subsequently; for the detailed characterizations of surface morphology, texture and; optical property respectively. It was observed that the as-prepared; Cu_2O PNFs exhibited flexible porosities and nanosize building units,; which were greatly dependent on the substrate negative bias voltage. In; particular, when the substrate bias voltage was kept at -50 or -150 V,; the as-prepared Cu_2O PNFs both demonstrated intriguing triangular; pyramid-like nanostructures with distinct edges and corners on the; porous film surface. Further, the side view FESEM images and the; out-of-plane GIXRD spectra demonstrated a columnar growth of the Cu_2O; PNFs with a notable preferential orientation of (111). The optical; testing results showed that the band gap of the Cu_2O PNFs obtained at; different negative bias voltages was tunable between 2.0 and 2.35 eV,; which demonstrated a little red or blue shift relative to that of bulk; Cu_2O (2.17 eV). It is expected that the traditional ion bombardment and; re-sputtering theories are not suitable for the explanation of the above; bias voltage effects. This is because the traditional ion bombardment; and re-sputtering theories were proposed to account for the bias; deposition in an unbalanced magnetron sputtering (MS) system rather than; the present balanced MS system. Further, the experimentally observed; non-linearly changed density or porosity of the Cu_2O PNFs with the bias; voltage at relatively low values and the common even surface at; relatively high values confirmed this viewpoint. Based on the above; findings and analysis, a selectively preferential deposition of material; atoms or molecules on the film surface during the negative bias; deposition was proposed. That is, when the substrate is negatively; biased, the tipcharging effect of electrons would occur on the nanoscale; rough surface of the substrate or the depositing film. The resulting; electric field near the substrate or film surface is non-uniform and; could be regarded as an assembly of many electric fields of particle or; tip charges.国家自然科学基金; 江苏省自然科学基金; 江西省教育厅科技项目; 江西省自然科学基