Surface Modification of Oxide Nanowires by Nitrogen Plasma

Abstract

The amount of oxygen vacancies on the surface of SnO 2 nanowires was controlled by N 2 plasma. Nitrogen ions in N 2 plasma were substituted for oxygen vacancies (V o ) on the nanowire surface, reducing the amount of oxygen vacancies. Photoluminescence spectra showed that the V o -related peak around 600 nm decreased dramatically after N 2 plasma and increased again after ultravioletozone (UVO) treatment. The threshold voltage (V th ) of the SnO 2 nanowire transistors exhibited a þ1.8 V positive shift after N 2 plasma, and the V th of the N 2 plasma-treated nanowire transistors shifted toward the negative direction (À0.76 V) again after UVO.Oxide nanowires are applied in various fields including nanoscale electronics, next-generation displays, photovoltaic devices, and gas/solar sensors due to their outstanding characteristics such as wide-energy band gaps, nano-scale integration, optical transparency, mechanical flexibility, low voltage operation, and high mobility. [1][2][3][4] Most notably, studies are currently focusing on oxide nanowires applied to commercial electronic circuits and, in particular, integrated transistor circuits. 5-7 For such applications, it is crucial to effectively control the transistor characteristics of the oxide nanowires to meet required specifications of integrated transistor circuits. Therefore, nanowire characteristics should be controlled and monitored continuously through a device optimization process. In related studies, various methods, such as optimizing the growth conditions of nanowires, doping nanowires with various materials, and controlling characteristics through post-treatments after producing nanowire devices, are being applied. 8-10 Among these methods, post-treatments are relatively simple, easy to control, and ensure reproducibility. Various attempts have recently been made to control characteristics through post-treatment of the nanowire surface using thermal annealing, H 2 , O 2 , Ar plasma, and ozone treatment. In an oxygen atmosphere, the field emission of ZnO was enhanced through thermal annealing. 11 ZnO nanowire treated by Ar or H 2 plasma showed improved conductivity. 12,13 In addition, surface treatment using ultraviolet (UV) radiation enabled temporary interface treatment. 14 However, these attempts were only applied to the observation of nanowire properties after the posttreatment, not to the fine control of the characteristics of nanowire devices.In this study, N 2 plasma was used to control the characteristics of SnO 2 nanowire transistors (NWTs) by controlling the characteristics of the SnO 2 nanowire surface. The amount of oxygen vacancies (V o ), which act as current paths in semiconducting oxide nanowires, were determined during the initial growth stage of crystal formation; this stage determines the threshold voltage (V th ), subthreshold slope (SS), and mobility characteristics of oxide NWTs. But, N 2 plasma successfully controlled transistor characteristics of NWT devices, including V th , by controlling V o on the surface of oxide nanowires afte...

Tin oxide and indium oxide nanowire transport characteristics: influence of oxygen concentration during synthesis

“…Oxygen vacancies are common defects in nanocrystalline oxides affecting electronic transport and optical properties. When faced with such defects in oxide nanowires, post-processing techniques such as nitrogen plasma treatment [30], laser annealing [10] and thermal annealing [31,32] have been used to reduce or eliminate oxygen vacancies and recover device performance. However, it is desirable to control these defects during the growth process itself; while the numerous process parameters mentioned earlier do not appear to have an effect, the impact of oxygen content in the input gas stream has not been studied much.…”

Metallic, Linear, and Saturated Output Characteristics of Oxide Nanowire Transistors

“…An oxygen vacancy is a donor type defect, which is different from defects that interfere with the movement of electrons and result in a decreased mobility and conductivity. Oxygen vacancies are known to play a role as electron donors in oxide nanowire channels and in the passage of current flow [15], [16], and this is assumed to be one of the main reasons for the change of the transistor characteristics. Thus, if the distribution and generation rate of the oxygen vacancies are varied by the process conditions or growth environment during the growth of the oxide nanowire, the basic characteristics of the oxide nanowire will be changed along with the transistor characteristics.…”

Aligned Circular-Type Nanowire Transistors Grown on Multilayer Graphene Film

“…As the number of oxygen vacancies increases, conductivity improves and V th decreases. 35 Therefore, it is assumed that V th exhibited significant negative shifts, as a large number of oxygen vacancies were formed in the SnO 2 nanowires.…”

“…Because an oxygen vacancy plays the role of an electron donor in a nanowire transistor, , the electrical characteristics change according to the level of oxygen vacancy. As the number of oxygen vacancies increases, conductivity improves and V th decreases . Therefore, it is assumed that V th exhibited significant negative shifts, as a large number of oxygen vacancies were formed in the SnO 2 nanowires.…”