Controllable Formation of (004)-Orientated Nb:TiO₂ for High-Performance Transparent Conductive Oxide Thin Films with Tunable Near-Infrared Transmittance

Abstract

A niobium-doped titanium dioxide (Nb:TiO, NTO) film is a promising candidate material for indium-free transparent conductive oxide (TCO) films. It is challenging and interesting to control (004)-oriented growth to decrease resistivity. In this work, NTO films with different fractions of preferential (004) orientation (η) were controllably prepared by direct current sputtering. Notably, the direction of local-ordering of ions-packing could be adjusted by slightly changing the angle between the sputtering source and the glass substrate, which is identified as a key factor to determine the growth direction of a columnar crystal as well as the η of films. Hall effect measurements indicate that NTO films with the highest η present the lowest resistivity (6.4 × 10 Ω cm), which originates from super-high carrier concentration (2.9 × 10 cm) and mobility (3.4 cm V s). The corresponding low sheet resistance (10.3 Ω sq) makes it a potential material for commercial TCO films. We also observe that films with higher η show lower transmittance in the near-infrared region.

Highly crystalline Nb-doped TiO2 nanospindles as superior electron transporting materials for high-performance planar structured perovskite solar cells

“…Up to now, magnesium, 18 lithium or sodium, [19][20][21][22] samarium, 23 lanthanum, 24 tantalum, 25 uorine, 26 thallium, 27 and other metal [28][29][30] doped TiO 2 have been attempted in perovskite solar cells. Niobium-doped TiO 2 (Nb:TiO 2 ) has been tremendous used in transparent conductive oxides (TCOs), 31 photocatalysis, 32,33 lithium and sodium ion batteries, 34,35 dyesensitized solar cells (DSSCs). [36][37][38][39][40][41][42] However, limited work on Nb:TiO 2 has been performed in planar PSCs to date.…”

Preparation of High-Performance Metal-Free UV/Near Infrared-Shielding Films for Human Skin Protection

“…The XRD patterns exhibited a higher intensity of the (101) peak than other peaks, revealing the stronger tendency of the TiO 2 crystallites to grow with a preferred (101) orientation. According to thermodynamics, a TiO 2 structure with (101) orientation is more stable because of its lower surface free energy over that of a structure with (100) orientation [ 28 ]. Thus, the anatase-phase TiO 2 films grew preferably along the [101] axis in the direction perpendicular to the glass substrate.…”

“…Moreover, the (101) lattice plane grew perpendicular to the film growth direction, leading to a (101)-textured microstructure. As the (101) plane of TiO 2 is thermodynamically stable because of its lower surface free energy than those of other planes [ 28 ], the adatoms on the (101) crystalline plane diffuse faster, resulting in the growth of grains with (101) orientation. These results are consistent with the XRD results of the TiO 2 films.…”

Seed-Mediated Growth of Conductive and Transparent Anatase Nb-TiO2 Films for CdS-Based Devices

“…The resistivity of NTO film is related to the crystal phase and orientation. Generally, rutile suppresses the conductivity compared to anatase , and the (004) orientation shows higher electron mobility than the other orientations due to the static effective mass along the a -axis ( m (100) *) is smaller than that along the c -axis ( m (001) *). , Thus, a high Hall mobility of 6.85 cm 2 /(V s) is obtained in the seed-mediated NTO samples which is higher than those in literatures (mostly between 2 and 5 cm 2 /(V s)). , The carrier concentrations have a direct relationship with the oxygen vacancies. Thus, XPS was performed on those annealed samples and shown in Figure S5 in the Supporting Information.…”

“…Seed-mediated growth is a common strategy to produce a particular phase, and it should be feasible to achieve orientated film growth using this concept. According to the film growth theory, the crystal faces or phase structures with the smallest Gibbs free energy are preferred for nucleation and crystallization based on the minimum energy principle. , The Gibbs free energy includes not only the kinetic energy of the depositing particles but also the surface energy produced at the heterointerface, which may be dominant especially in the beginning of deposition. , As the film thickens, the interface effect weakens and the Gibbs free energy is dominated by the kinetic energy of the depositing particles again. Therefore, exploiting this energy evolution with film thickness and precise energy control of the incident particles, special crystalline seeds can be created at the heterointerface.…”