This paper reports a systematic study on the relationship between surface structure and wetting state of ordered nanoporous alumina surface. The wettability of the porous alumina is dramatically changed from hydrophilicity to hydrophobicity by increasing the hole diameter, while maintaining the hole interval and depth. This phenomenon is attributed to the gradual transition between Wenzel and Cassie states which was proved experimentally by comparing the wetting behavior on these porous alumina surfaces. Furthermore, the relationship between surface wettability and hole depth at a fixed hole interval and diameter was investigated. For those porous alumina with relatively larger holes in diameter, transition between Wenzel and Cassie states was also achieved with increasing hole depth. A capillary-pressure balance model was proposed to elucidate the unique structure-induced transition, and the criteria for the design and construction of a Cassie wetting surface was discussed. These structure-induced transitions between Wenzel and Cassie states could provide further insight into the wetting mechanism of roughness-induced wettability and practical guides for the design of variable surfaces with controllable wettability.

Fabrication and Characterization of the Memory Device: The indium tin oxide (ITO)/glass substrate was pre-cleaned with water, acetone, and isopropanol, in that order, in an ultrasonic bath for 15 min. A toluene solution of PKEu (15 mg mL ±1 ) was spin-coated onto ITO, followed by solvent removal in a vacuum chamber at 10 ±5 torr (1 torr = 133 Pa) at room temperature. The thickness of the polymer layer was about 50 nm. Finally, the 100 nm thick square Al electrodes for needle contacts were thermally evaporated at a pressure around 10 ±7 torr. Cyclic voltammetry (CyV) was performed using an Autolab potentiostat/galvanostat under an argon atmosphere. Transmission electron microscopy (TEM) measurements were carried out on a JEOL JEM-2010F field emission electron microscope equipped with a GATAN Multiscan camera. Other electrical measurements were carried out on a HP 4156A semiconductor parameter analyzer under ambient conditions. Data storage using scanning probe microscopy (SPM) has attracted a great deal of attention because of its nanometer-scale storage capacity.[1] In principle, SPM memory has the potential to achieve a storage density of 6 Pb in ±2 (»0.9 Pb cm ±2; Pb = petabits) when using an atom or a vacancy as an information bit. Among the varieties of SPM storage methods proposed in the last decade, the use of a scanning tunneling microscopy (STM) tip current as a nanometer-sized heater to induce a localized physical change of the storage media for data writing, bears resemblance to methods for making commercial magneto-optic (MO) and phase-change disks.[2] Previous experimental and theoretical studies have demonstrated the feasibility of such kinds of thermophysical STM storage techniques. [2,3] Herein, we report a novel STM-based thermochemical technique for realizing ultrahigh-density data storage. The basic idea is to use the heating effect of the current from an COMMUNICATIONS

The present article describes a thermochemical hole burning (THB) effect on a charge-transfer complex triethylammonium bis-7,7,8,8-tetracyanoquinodimethane (TEA(TCNQ)(2)) using single-walled carbon nanotube (SWNT) scanning tunneling microscopy (STM) tips, which demonstrates the possibility of optimizing the THB storage materials and the writing tips for ultrahigh-density data storage. TEA(TCNQ)(2) is proven to be a high-performance THB storage material, which gives deeper holes and larger hole depth-to-diameter ratio as compared to the previous materials dipropylammonium bis-7,7,8,8-tetracyanoquinodimethane and N-methyl-N-ethylmorpholinium bis-7,7,8,8-tetracyanoquinodimethane. Instead of conventional Pt/Ir STM tips, SWNT tips made by a unique chemical assembly technique we developed have been shown to be excellent writing tips for greatly decreasing the hole sizes and increasing the storage density. Possible reasons for the improvements on the storage performance were discussed.

We demonstrate here the thermochemical hole burning (THB) effect on a series of N-substituted morpholinium 7,7,8,8-tetracyanoquinodimethane charge-transfer (C-T) complexes for ultra-high-density data storage. A correlation between the decomposition temperature of the charge-transfer complex and the threshold voltage of hole burning was observed: the higher the decomposition temperature, the larger the writing threshold value, suggesting the possibility of molecular design for optimizing the hole burning performance. The macroscopic decomposition properties of these charge-transfer complexes were studied by thermal gravimetry combined with mass spectrometry. Theoretical estimation of the temperature rise induced by scanning tunneling microscopy current heating was also conducted, which indicated that the maximum temperature certainly exceeds the decomposition temperatures of these C-T complexes. These observations are consistent with the thermochemical hole burning mechanism.

A thermochemical hole burning (THB) effect was observed on two organic charge transfer complexes, when applying a suitable voltage pulse using a scanning tunneling microscope (STM), which is closely related to a STM current-induced localized thermochemical decomposition of the charge-transfer complex. The decomposition reaction evolves the low boiling point decomposition components of the charge-transfer complex, leaving a nanometer-sized hole on the crystal surface. This effect demonstrates the possibility of creating an ultrahigh-density THB memory, in which information bit is recorded as a hole.