1 ± 0.1 eV and 486.6 ± 0.1 eV, correspond to the Sn4+ ion, respectively, which are relative to the electrical conduction of the nanowires [28]. The O 1s peak is deconvoluted by a Gaussian function into three positions. The lower binding energy component at 530 ± 0.1 eV is due to the O2− ions whose neighboring indium atoms are surrounded by the six nearest O2− ions. The medium binding energy at 531.3 ± 0.1 eV corresponds to the oxygen deficiency

regions, which are called oxygen vacancies [28, 29]. The higher binding energy at 532.6 ± 0.1 eV is associated Chk inhibitor with the oxygen of free hydroxyl group, which is possibly due to the water molecules absorbed on the surface [30]. All XPS results show that Sn atoms are doped into the In2O3 NWs with the existence of oxygen vacancies. Consequently, the oxygen vacancies and Sn ions contribute the electron concentration to the NWs, resulting in an n-type semiconducting behavior. Figure 3 XRD spectra and high-resolution TEM image. (a) XRD spectra of ITO NWs. (b) A high-resolution

TEM image of ITO nanowire. The inset shows a corresponding selective area diffraction pattern, revealing that [100] is a preferred growth direction. (c) Chemical bonding information Y-27632 solubility dmso of In, Sn, and O for the ITO NWs extracted from the XPS spectra. Figure 4a shows field emission properties of the ITO NWs grown on Au film and patterned Au film with growth time of 3 and 10 h, respectively. The turn-on field (E on) is defined as the electric field required for generating a current density of 0.01 mA/cm2, and 0.1 mA/cm2 is sufficient for operating display panel devices. It is found that the turn-on field decreases from 9.3 to 6.6 V μm−1 after the selective area growth of ITO NWs at the growth time of 3 h. Insets in Figure 4b reveal a linear relationship, so-called ln(J/E 2)-(1/E) plot, indicating that the field-emission behavior follows Fowler-Nordheim Ceramide glucosyltransferase relationship, i.e., electrons tunneling through a potential barrier, which can be expressed as follows [31–33]: (7) where J is the emission current density; E, the applied field; ϕ, the work function of emitter material; β, the enhancement factor; A, constant (1.56

× 10−10 A V−2 eV); and B, constant (6.8 ×103 eV−3/2 V μm−1) The field enhancement factor, β, reflects the degree of the field emission enhancement of the tip shape on a planar surface, which is also dependent on the geometry of the nanowire, the crystal structure, and the density at the emitting points. It can be determined by the slope of the ln(J/E 2)-(1/E) plot with a work function value of 4.3 eV [6]. Consequently, the turn-on fields and the β values of the ITO NWs with and without selective area growth at different growth times are listed in Table 1. Obviously, the field enhancement factors (β) from 1,621 to 1,857 can be achieved after the selective area growth at 3 h. Moreover, we find that the screen effect also highly depends on the length of nanowires on the field emission performance.