Controllable Formation of Nanoscale Patterns on TiO₂ by Conductive-AFM Nanolithography

Abstract

We report on the nanopatterning of double-bond-terminated silane (5-hexenyltrichlorosilane, HTCS) molecules on titania (TiO2) using conductive atomic force microscopy (AFM). The influences of tip electrostatic potential and scanning velocity, relative humidity and of the repeated application of voltage on the topographic height, width, and hydrophilic and hydrophobic contrast of the resultant patterns were investigated. Tip voltage and tip velocity ( v) were applied between -10 V <or= V tip <or= +10 V and 100 nm/s <or= v <or= 2 microm/s during the lithography step(s), respectively. Average height and Lateral Force Mode (LFM) images of patterns were obtained with different values of (-10 V <or= V tip <or= -7 V) and v (100 nm/s <or= v <or= 2 microm/s). The average height of the patterns is seen to decrease for increasing v and decreasing V tip in both a single or repeated lithography step. No patterns were observed following a single or repeated lithography step for -5 V <or= V tip <or= +10 V. This conductive lithography technique results in nanoscale physiochemical manipulations of the HTCS molecules that are manifested as controllable step heights ranging from approximately 1-15 nm possessing different chemistries on the patterned and unpatterned areas. The use of conductive-AFM nanolithography for altering and manipulating double-bond-terminated molecules on TiO2 surfaces suggests a range of applications, including selective immobilization and assembly of functionalized inorganic nanoparticles and biomolecules.

Removing Material Using Atomic Force Microscopy with Single‐ and Multiple‐Tip Sources

“…If AFM tips are used to perform electro‐induced material removing processes, such as EIA and ECN, which were presented in Section 5.3 and 5.5, respectively, they have to be conductive or semiconductive. AFM involving a conducting tip is also called conductive AFM; the tip conductivity in addition to the tip geometry can influence the performance of the designated AFM activities 18. To make the probe conductive, the tip side of the cantilever is frequently coated with a highly conductive metal.…”

“…The backside can also be coated by a highly reflective metal to improve the reflection of the PSD laser beam. The reflective coating is typically made of Pt or Au with an additional interface thin film, such as iridium or chromium, to improve its adhesion to a Si‐ or Si 3 N 4 ‐based probe 18, 19. Tips made of high‐conductivity and high‐hardness materials, such as diamond and CNT (carbon nanotubes), may also be used for conductive AFM 19…”

Photo-induced hybrid nanopatterning of titanium dioxide via direct imprint lithography

“…9 Various fabrication methods for the nanopatterning of TiO 2 thin films as well as template nanofabrication have been studied extensively due to the trend towards the miniaturization of device components. 10,11 While previously reported conventional methods such as electronbeam lithography, 12 atomic force microscopy (AFM) nanolithography, 13 and ion beam lithography can be used for the fabrication of nanopatterned TiO 2 thin films, 14 they are too costly to use in many applications. Furthermore, a number of drawbacks remain, such as low throughput and unsuitability of these methods for large-area patterning.…”

The use of time resolved aerosol assisted chemical vapour deposition in mapping metal oxide thin film growth and fine tuning functional properties

“…The initial hydrophobicity observed for all samples is characteristic of nanoscale monolithic growths found in previous studies on a range of materials which also exhibit nanoscale (100 nm) monolithic surface morphology. [32][33][34][35] due to nanoscale monoliths present in surface morphology the surface exhibits a high degree of roughness. 36…”