Study of nitrogen ion doping of titanium dioxide films

Abstract

This study reports on the properties of nitrogen doped titanium dioxide (TiO 2 ) thin films considering the application as transparent conducting oxide (TCO). Sets of thin films were prepared by sputtering a titanium target under oxygen atmosphere on a quartz substrate at 400 or 500°C. Films were then doped at the same temperature by 150 eV nitrogen ions. The films were prepared in Anatase phase which was maintained after doping. Up to 30at% nitrogen concentration was obtained at the surface, as determined by in situ x-ray photoelectron spectroscopy (XPS). Such high nitrogen concentration at the surface lead to nitrogen diffusion into the bulk which reached about 25 nm. Hall measurements indicate that average carrier density reached over 10 19 cm -3 with mobility in the range of 0.1 to 1 cm 2 V -1 s -1 . Resistivity about 3.10 -1 cm could be obtained with 85% light transmission at 550 nm. These results indicate that low energy implantation is an effective technique for TiO 2 doping that allows an accurate control of the doping process independently from the TiO 2 preparation. Moreover, this doping route seems promising to attain high doping levels without significantly affecting the film structure. Such approach could be relevant for preparation of N:TiO 2 transparent conduction electrodes (TCE). Graphical abstractHighlights  A two-step process for preparation of N:TiO 2 transparent conductor is proposed. Low energy nitrogen ions are used after Anatase thin film deposition. Approach allows excellent control of crystal, optical and electronic properties.  Resistivity as low as 3.10 -1 cm while transparency at 550nm is about 85%.

Revealing the true impact of interstitial and substitutional nitrogen doping in TiO2 on photoelectrochemical applications

“…The additional N 1s peak at ~396.1 eV for TN-500 is associated to the substitutional N doping. 24,43,51,54 The N 1s spectra of TN-600 was much different than TN-400 and TN-500, as an additional peak at 396.9 eV was present due to the formation of TiN (also seen in XRD and HRTEM). Additionally, the peak related to N substitution increased in intensity, compared to the interstitial peak, demonstrating higher N doping for TN-600 when compared with TN-500.…”

“…36 Furthermore, if N 3replaces O 2the charge balance will necessitate the removal of three O ions from the TiO2 lattice to replace them with two N ions. 24,27 Thus, TiO2 will consist of O vacancies and reduced species (e.g Ti 3+ (Figure 4)) which form donor states below the CB of TiO2. 53 Therefore, the overall effect of N doping in the electronic structure of TiO2 is to generate donor levels (due to the O vacancies and Ti 3+ species) below CB and acceptor states above the VB (due to N substitutional/interstitial defects).…”

“…7,17,18 The most common approaches to prepare N doped TiO2 are magnetron sputtering, 19,20 annealing in a N2 or NH3 flux, 21,22 washing with nitrogen precursors 23 and ion implantation. 24 It has been suggested that the N atoms substitute oxygen atoms in the TiO2 lattice and new N 2p states are introduced that can be either shallow or deep level states. 25 Both states can extend the spectral range for light absorption to longer wavelengths.…”

Ion‐Implantation in Titania‐Based Plasmonic Photo‐anodes: A Review

“…Among the metal-oxide semiconductors, TiO 2 has been considered to be the benchmark material for photo-catalytic and photo-electrochemical applications and has been studied over the decades. [8,56,261,262] TiO 2 is widely researched for these applications, owing to its notable material properties and cost effectiveness. [1,24,74,263] Researchers can refer to the earlier published excellent articles for a detailed introduction to photo-catalysis.…”

Turning on the Photoelectrochemical Responses of Cd Probe-Deposited g-C3N4 Nanosheets by Nitrogen Plasma Treatment toward a Selective Sensor for H2S

“…To date, the modification strategies of nonmetallic doping have been widely applied for the fabrication of various photocatalysts to improve their photomotivated activities. − As the popular representative, the nitrogen (N) doping modification routes for photocatalysts are conventionally performed through high-temperature calcination typically using some nitrogenous organics as precursors. , However, the formidable agglomeration of nanomaterials during the calcination may take place to influence the catalysis activities of the catalysts. In recent years, the gas-derived plasma treatment technologies with some distinctive characteristics such as simple operation, rapid processing, and high efficiency have been applied alternatively for the modification or treatment of photocatalysts toward improved surface properties. , In particular, N 2 can be activated under plasma conditions to produce high-energy plasma (N + and N 2+ ) for doping N contents onto the nanomaterials. , Yet, the employment of the N 2 plasma pretreatment of g-C 3 N 4 nanosheets for the synergistic deposition of Cd probe toward the construction of photocatalytic heterojunctions has rarely been reported to date.…”