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In van der Waals (vdW) heterostructures formed by stacking two monolayer semiconductors, lattice mismatch or rotational misalignment introduces an in-plane moire superlattice. While it is widely recognized that a moire superlattice can modulate the electronic band structure and lead to novel transport properties including unconventional superconductivity and insulating behavior driven by correlations, its influence on optical properties has not been investigated experimentally. We present spectroscopic evidence that interlayer excitons are confined by the moire potential in a high-quality MoSe2/WSe2 heterobilayer with small rotational twist. A series of interlayer exciton resonances with either positive or negative circularly polarized emission is observed in photoluminescence, consistent with multiple exciton states confined within the moire potential. The recombination dynamics and temperature dependence of these interlayer exciton resonances are consistent with this interpretation. These results demonstrate the feasibility of engineering artificial excitonic crystals using vdW heterostructures for nanophotonics and quantum information applications.

Lateral force microscopy (LFM) is used to examine friction at the nanoscale. Although the friction at the tip-sample contact measured by LFM can provide extensive information beyond the friction force itself, such as the crystallographic orientation, the presence of defects, etc., there have been many contradictory reports regarding friction coefficients, nanoscale friction laws, etc. obtained by this technique. Here we investigate the effect of scan rate and gain on the LFM frictional force measurements. We show that the ratio of friction measured on SiO2 to friction measured on graphene can vary from about 1 to approximately 9.2 depending on the combination of these parameters. We discuss how to optimize the associated scan parameters to obtain reliable friction data at the nanoscale.

For comparative friction studies, a reference sample, which holds stable and reproducible frictional characteristics, is required. Here, we have studied the frictional properties of native silicon oxide and silicon oxide formed through wet thermal oxidation by using lateral force microscopy. Once cleansed using solvents such as acetone, the friction measured on these frequently-used reference materials undergoes gradual change by a series of scanning. The friction is observed to increase with the number of scans and reaches about 1.5 times the initial value. We find that soft baking at 150 °C - 200 °C for 30 minutes can eliminate this problem.

Using a multi-walled carbon nanotube (MW-CNT) tip, we have observed the honeycomb lattice of highly oriented pyrolytic graphite (HOPG) via scanning tunneling microscopy (STM). This observation was made after acquiring typical STM images of HOPG, i.e., showing the triangular lattice. We consider this change is due to atomic reconfiguration at the apex of the MW-CNT tip induced by continuous STM scanning. The atomic-level sharpening of CNT tips will be useful to image samples with small lattice constants or to obtain orbital information from samples with an orbital ordering such as manganites.

Interlayer exciton diffusion in transition metal dichalcogenide heterostructures is controlled by the moiré potential., The properties of van der Waals heterostructures are drastically altered by a tunable moiré superlattice arising from periodically varying atomic alignment between the layers. Exciton diffusion represents an important channel of energy transport in transition metal dichalcogenides (TMDs). While early studies performed on TMD heterobilayers suggested that carriers and excitons exhibit long diffusion, a rich variety of scenarios can exist. In a moiré crystal with a large supercell and deep potential, interlayer excitons may be completely localized. As the moiré period reduces at a larger twist angle, excitons can tunnel between supercells and diffuse over a longer lifetime. The diffusion should be the longest in commensurate heterostructures where the moiré superlattice is completely absent. Here, we experimentally demonstrate the rich phenomena of interlayer exciton diffusion in WSe2/MoSe2 heterostructures by comparing several samples prepared with chemical vapor deposition and mechanical stacking with accurately controlled twist angles.

One of the most pressing technological challenges in the development of next generation nanoscale devices is the rapid, parallel, precise and robust fabrication of nanostructures. Here, we demonstrate the possibility to parallelize thermochemical nanolithography (TCNL) by employing five nano-tips for the fabrication of conjugated polymer nanostructures and graphene-based nanoribbons.

Null imaging ellipsometry was developed to show the net change in polarization state between two samples. This system has no moving parts for nulling and does not exhibit azimuthal dependence on the optical elements. Therefore, this system is fast in data acquisition and easy to operate. In addition, image uniformity can be improved through a normalization process. For a demonstration, this system was applied to annealing studies of indium oxide thin films. The results show that this system can visualize the temperature dependence of the annealing as well as the progress of the annealing over time.Null imaging ellipsometry was developed to show the net change in polarization state between two samples. This system has no moving parts for nulling and does not exhibit azimuthal dependence on the optical elements. Therefore, this system is fast in data acquisition and easy to operate. In addition, image uniformity can be improved through a normalization process. For a demonstration, this system was applied to annealing studies of indium oxide thin films. The results show that this system can visualize the temperature dependence of the annealing as well as the progress of the annealing over time.

Density functional theory calculations are carried out to model the structure and interpret recent X-ray photoelectron spectroscopy measurements of graphene oxide films obtained by Hummers oxidation of multilayer graphene grown epitaxially on silicon carbide. The confrontations between theory and experiment are used to gain insight into the nature and fraction of the oxygen functional groups present in the oxide films. The study shows that this type of graphene oxide films includes small amounts of intercalated water molecules, ether groups, and doubly oxidized carbon species and that the oxidized graphene sheets encompass a disordered and homogeneous distribution of epoxide and hydroxyl species. The results of our spectral analysis are corroborated by a study of the energetic stability of water in this form of graphene oxide.

International audience; Graphene oxide has multiple potential applications. The chemistry of graphene oxide and its response to external stimuli such as temperature and light are not well understood and only approximately controlled. This under- standing is crucial to enable future applications of this material. Here, a com- bined experimental and density functional theory study shows that multilayer graphene oxide produced by oxidizing epitaxial graphene via the Hummers method is a metastable material whose structure and chemistry evolve at room temperature with a characteristic relaxation time of about one month. At the quasi-equilibrium, graphene oxide reaches a nearly-stable reduced O/C ratio, and exhibits a structure intensively deprived of epoxide groups and enriched of hydroxyl groups. Our calculations show that the structural and chemical changes are driven by the availability of hydrogen in the oxidized graphitic sheets, which favors the reduction of epoxide groups and the formation of water molecules.

The frictional properties of individual carbon nanotubes (CNTs) are studied by sliding an atomic force microscopy tip across and along its principle axis. This direction-dependent frictional behavior is found to correlate strongly with the presence of structural defects, surface chemistry, and CNT chirality. This study shows that it is experimentally possible to tune the frictional/adhesion properties of a CNT by controlling the CNT structure and surface chemistry, as well as use friction force to predict its structural and chemical properties., Comment: 6 pages, 3 figures, 2 tables

Graphene oxide holds great promise for future applications in nano-technology. The chemistry of this material is not well understood. This understanding is crucial to enable future applications of graphene oxide. In this study, experiments and density functional theory calculations are combined to elucidate the chemical properties of multilayer graphene oxide obtained by oxidizing epitaxial graphene grown on silicon carbide via the Hummers method. This study shows that at room temperature as prepared graphene oxide films exhibit a uniform and homogeneous structure, include a minimal amount of edges and holes, and have an oxidation ratio of about 0.44. The comparison with density-functional calculations shows that graphene oxide includes a minimal amount of intercalated water molecules and well-defined fractions of epoxide and hydroxyl groups.

The ability to create graphene nanoribbons with atomically sharp edges is important for various graphene applications because these edges significantly influence the overall electronic properties and support unique magnetic edge states. The discovery of graphene self-folding induced by traveling wave excitation through atomic force microscope scanning under a normal force of less than 15 nN is reported. Most remarkably, the crystallographic direction of self-folding may be either along a chosen direction defined by the scan line or along the zigzag or armchair direction in the presence of a pre-existing crack in the vicinity. The crystalline direction of the atomically sharp edge is confirmed via careful lateral force microscopy measurements. Multilayer nanoribbons with lateral dimensions of a few tens of nanometers are realized on the same graphene sheet with different folding types (e.g., z-type or double parallel). Molecular dynamics simulations reveal the folding dynamics and suggest a monotonic increase of the folded area with the applied normal force. This method may be extended to other 2D van der Waals materials and lead to nanostructures that exhibit novel edge properties without the chemical instability that typically hinders applications of etched or patterned graphene nanostructures.

III-V materials are considered as alternative channel materials to silicon beyond the 22 nm CMOS technology node due to their high electron mobility. However, the fabrication of high-performance III-V MOSFETs has long been elusive, primarily due to the lack of a high-quality native oxide for IIIVs analogous to that of silicon. Therefore, there has been an enormous effort to identify thermodynamically stable dielectrics which can also unpin the Fermi level. This includes the use of aSi and a-Ge interfacial layers, molecular beam epitaxy (MBE) grown Ga2O3(Gd2O3) and atomic layer deposition (ALD) of Al2O3 and HfO2. It is known that arsenic oxides are the potential cause of the Fermi level pinning in III-V MOS structures. Therefore, eliminating III-V native oxides at the interface of high-k/III-V layer is extremely crucial. On the other hand, integrating ALD high-k on III-V necessitates an effective surface chemical treatment, in order to mitigate the strong Fermi level pinning at the high-k/III-V interface. This surface treatment should also facilitate achieving full surface coverage from the beginning of the ALD run, while ruling out the re-growth of native oxides during the ex situ sample transfer to the ALD reactor. We have recently demonstrated that employing a simple wet clean in dilute HF followed by sulfur passivation in (NH4)2S can effectively improve the electrical characteristics of GaAs MOS capacitors. Moreover, the selective reduction and subsequent removal of GaAs native oxides upon ALD of high-k using an appropriate choice of precursor chemistry can eliminate the need for an elaborate in situ clean prior to the deposition of the high-k layer. In this work, we have examined the interfacial selfcleaning attribute of ALD-Al2O3 and HfO2 on GaAs substrates using trimethyl aluminum (TMA) and tetrakis (ethylmethyamido) hafnium (TEMAH) precursors by x-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Capacitance-voltage (C-V) characteristics of GaAs MOS capacitors with HfAlO gate dielectrics were monitored. Furthermore, we report the fabrication of n-channel self-aligned inversion-type enhancement-mode (E-mode) GaAs MOSFETs with ALD-Al2O3 gate dielectric directly on GaAs. In order to examine the interfacial self-cleaning attribute of ALD-Al2O3 and HfO2 using TMA and TEMAH precursors respectively, 2-nm thick high-k layers were grown on p-type GaAs substrates with no chemical treatment. Figure 1(a), (b) illustrate the corresponding As 3d spectra of the samples with ALD-Al2O3 and HfO2 dielectrics respectively before and after the high-k deposition, confirming the removal of As-O bonding upon ALD of these high-k layers. However, unlike the observed significant reduction of arsenic oxides, the level of Ga-O bonding remained almost unchanged. GaAs MOS capacitors were fabricated on p-type substrates with a doping concentration of 0.5-1×10 cm. A wet clean recipe was employed using a combination of HF-dip and sulfur passivation in (NH4)2S (20%). Next, 65A thick ALD-HfAlO gate dielectric was deposited at 250C, followed by TaN metal gate sputtering and patterning. The XPS analysis on the sulfide treated samples confirmed the absence of arsenic oxides as well as a significant reduction in the level of Ga-O bonding with respect to the non-treated samples. Furthermore, TEM studies revealed an abrupt highk/GaAs interface. Figure 2(a), (b) show the frequency dispersion behavior of an MOS capacitor at room temperature and 150C. It has been reported that interface states at a very small portion of the GaAs bandgap will be probed by monitoring the RT frequency dispersion behavior. Hence, performing an additional measurement at 150C is essential in order to safely conclude low midgap interface trap density (Dit). However, we observed an increase in the dispersion of the C-V curves at 150C with respect to the room temperature, implying a relatively high midgap Dit. The midgap Dit was measured to be 3-4×10 eV cm using ac-conductance method. Self-aligned E-mode n-channel GaAs MOSFETs were fabricated with ALD-Al2O3 gate dielectric, employing the same wet cleaning recipe. Source/drain (S/D) regions received a Si implant of 30keV with a dose of 1×10 cm. Dopant activation was carried out at 800C in N2 ambient. The threshold voltage and subthreshold slope were deduced to be 0.3V and ~145mV/dec from ID-VG characteristics. The maximum drive current at a gate overdrive of 2.0V for a MOSFET with a gate length of 5μm was measured to be ~16μA/μm. In summary, we have studied the chemical, physical and electrical properties of the interface between ALD-HfAlO gate dielectric and GaAs substrates. Self-aligned E-mode GaAs MOSFETs were successfully fabricated, confirming the effectiveness of the ex situ GaAs surface chemical treatment in mitigating the strong Fermi level pinning. This work was supported in part by DARPA and Micron Foundation.

We report on the first demonstration of controllable carbon doping of graphene to engineer local electronic properties of a graphene conduction channel using focused electron beam induced deposition (FEBID). Electrical measurements indicate that an "n-p-n" junction on graphene conduction channel is formed by partial carbon deposition near the source and drain metal contacts by low energy (50 eV) secondary electrons due to inelastic collisions of long range backscattered primary electrons generated from a low dose of high energy (25 keV) electron beam (1 × 10(18) e(-) per cm(2)). Detailed AFM imaging provides direct evidence of the new mechanism responsible for dynamic evolution of the locally varying graphene doping. The FEBID carbon atoms, which are physisorbed and weakly bound to graphene, diffuse towards the middle of graphene conduction channel due to their surface chemical potential gradient, resulting in negative shift of Dirac voltage. Increasing a primary electron dose to 1 × 10(19) e(-) per cm(2) results in a significant increase of carbon deposition, such that it covers the entire graphene conduction channel at high surface density, leading to n-doping of graphene channel. Collectively, these findings establish a unique capability of FEBID technique to dynamically modulate the doping state of graphene, thus enabling a new route to resist-free, "direct-write" functional patterning of graphene-based electronic devices with potential for on-demand re-configurability.

International audience; Two-dimensional materials, such as graphene and MoS 2 , are films of a few atomic layers in thickness with strong in-plane bonds and weak interactions between the layers. The in-plane elasticity has been widely studied in bending experiments where a suspended film is deformed substantially; however, little is known about the films' elastic modulus perpendicular to the planes, as the measurement of the out-of-plane elasticity of supported 2D films requires indentation depths smaller than the films' interlayer distance. Here, we report on sub-ångström-resolution indentation measurements of the perpendicular-to-the-plane elasticity of 2D materials. Our indentation data, combined with semi-analytical models and density functional theory, are then used to study the perpendicular elasticity of few-layer-thick graphene and graphene oxide films. We find that the perpendicular Young's modulus of graphene oxide films reaches a maximum when one complete water layer is intercalated between the graphitic planes. This non-destructive methodology can map interlayer coupling and intercalation in 2D films.

A novel coarse approach mechanism for a scanning tunneling microscope (STM) is described. Any approach mechanism, which brings a tip close to the sample, suffers from dry frictional force, which makes positioning of the tip over the sample rather difficult. In this unique design, we have reduced the friction to a minimum by oscillating the normal force on the sliding sapphire surfaces. This technique allows us to precisely position the tip over the sample after traveling a distance greater than 100 μm while maintaining a compact STM design. This technique of reducing friction is also very useful in an automatic inertial approach mechanism (or “stick–slip” motor), where the motion often becomes clamped due to excessive friction. We believe that this technique will be extremely useful for applications where high precision positioning is required.

International audience; The chemistry of graphene oxide (GO) and its response to external stimuli such as temperature and light are not well understood and only approximately controlled. This understanding is however crucial to enable future applications of the material that typically are subject to environmental conditions. The nature of the initial GO is also highly dependent on the preparation and the form of the initial carbon material. Here, we consider both standard GO made from oxidizing graphite and layered GO made from oxidizing epitaxial graphene on SiC, and examine their evolution under different stimuli. The effect of the solvent on the thermal evolution of standard GO in vacuum is first investigated. In situ infrared absorption measurements clearly show that the nature of the last solvent in contact with GO prior to deposition on a substrate for vacuum annealing studies substantially affect the chemical evolution of the material as GO is reduced. Second, the stability of GO derived from epitaxial graphene (on SiC) is examined as a function of time. We show that hydrogen, in the form of CH, is present after the Hummers process, and that hydrogen favors the reduction of epoxide groups and the formation of water molecules. Importantly, this transformation can take place at room temperature, albeit slowly (~ one month). Finally, the chemical interaction (e.g. bonding) between GO layers in multilayer samples is examined with diffraction (XRD) methods, spectroscopic (IR, XPS, Raman) techniques, imaging (APF) and first principles modeling.

A compact dual-tip scanning tunneling microscope (STM) design that achieves both rigidity and stability is presented. We constructed a prototype unit to perform tests in ambient conditions. The two STM tips were able to maintain a stable tunneling condition with the sample surface simultaneously. Topographic images of a fresh cleaved graphite were taken simultaneously from the two tips. A common feature found in both images indicates that the two tunneling spots are ~800 nm apart

Understanding and manipulating fluids at the nanoscale is a matter of growing scientific and technological interest. Here we show that the viscous shear forces in nanoconfined water can be orders of magnitudes larger than in bulk water if the confining surfaces are hydrophilic, whereas they greatly decrease when the surfaces are increasingly hydrophobic. This decrease of viscous forces is quantitatively explained with a simple model that includes the slip velocity at the water surface interface. The same effect is observed in the energy dissipated by a tip vibrating in water perpendicularly to a surface. Comparison of the experimental data with the model shows that interfacial viscous forces and compressive dissipation in nanoconfined water can decrease up to two orders of magnitude due to slippage. These results offer a new understanding of interfacial fluids, which can be used to control flow at the nanoscale.

We studied the ferromagnetic topology in a Y0.67Ca0.33MnO3 thin film with a combination of magnetic force microscopy and magnetization measurements. Our results show that the spin-glass like behavior, reported previously for this system, could be attributed to frustrated interfaces of the ferromagnetic clusters embedded in a non-ferromagnetic matrix. We found temperature dependent changes of the magnetic topology at low temperatures, which suggests a non-static Mn3+/Mn4+ ratio. Fil: Kim, Jeehoon. Los Alamos National High Magnetic Field Laboratory; Estados Unidos Fil: Haberkorn, Nestor Fabian. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Kim, Suenne. Georgia Institute of Technology; Estados Unidos Fil: Civale, L.. Los Alamos National High Magnetic Field Laboratory; Estados Unidos Fil: Dowden, P. C.. Los Alamos National High Magnetic Field Laboratory; Estados Unidos Fil: Movshovic, R.. Los Alamos National High Magnetic Field Laboratory; Estados Unidos

A complementary metal-oxide-semico-nductor (CMOS)-compatible method for the direct fabrication of arbitrary-shaped Pb(Zr0.52 Ti0.48)O3 and PbTiO3 ferroelectric/piezoelectric nanostructures on plastic, silicon, and soda-lime glass substrates is reported. Thermochemical nanolithography is used to induce nanoscale crystallization of sol-gel precursor films. Ferroelectric lines with width ≥30 nm, spheres with diameter ≥10 nm, and densities up to 213 Gb in(-2) are produced.

We demonstrate controlled manipulation of semiconductor and metallic nanoparticles (NPs) with 5-15 nm diameters and assemble these NPs into hybrid structures. The manipulation is accomplished under ambient environment using a commercial atomic force microscope (AFM). There are particular difficulties associated with manipulating NPs this small. In addition to spatial drift, the shape of an asymmetric AFM tip has to be taken into account in order to understand the intended and actual manipulation results. Furthermore, small NPs often attach to the tip via electrostatic interaction and modify the effective tip shape. We suggest a method for detaching the NPs by performing a pseudo-manipulation step. Finally, we show by example the ability to assemble these small NPs into prototypical hybrid nanostructures with well-defined composition and geometry.

Using atomic force microscopy nanomanipulation, we position a single Au nanoparticle near a CdSe/ZnS quantum dot to construct a hybrid nanostructure with variable geometry. The coupling between the two particles is varied in a systematic and reversible manner. The photoluminescence lifetime and blinking of the same quantum dot are measured before and after assembly of the structure. In some hybrid structures, the total lifetime is reduced from about 30 ns to well below 1 ns. This dramatic change in lifetime is accompanied by the disappearance of blinking as the nonradiative energy transfer from the CdSe/ZnS quantum dot to the Au nanoparticle becomes the dominant decay channel. Both total lifetime and photoluminescence intensity changes are well described by simple analytical calculations.

We investigate the emission dynamics of a single semiconductor quantum dot near a single Au nanoparticle. Due to coupling between the nanoparticles, the quantum dot exhibits a strong polarization dependence and reduced blinking.

International audience; Graphene's extraordinary physical properties and its planar geometry make it an ideal candidate for a wide array of applications, many of which require controlled chemical modification and the spatial organization of molecules on its surface. In particular, the ability to functionalize and micropattern graphene with proteins is relevant to bioscience applications such as biomolecular sensors, single-cell sensors, and tissue engineering.Wereport a general strategy for the noncovalent chemical modification of epitaxial graphene for protein immobilization and micropatterning. We show that bifunctional molecule pyrenebutanoic acid-succinimidyl ester (PYR-NHS), composed of the hydrophobic pyrene and the reactive succinimide ester group, binds to graphene noncovalently but irreversibly. We investigate whether the chemical treatment perturbs the electronic band structure of graphene using X-ray photoemission (XPS) and Raman spectroscopy. Our results show that the sp2 hybridization remains intact and that the π band maintains its characteristic Lorentzian shape in the Raman spectra. The modified graphene surfaces, which bind specifically to amines in proteins, are micropatterned with arrays of fluorescently labeled proteins that are relevant to glucose sensors (glucose oxidase) and cell sensor and tissue engineering applications (laminin).

Writing Conductive Lines with Hot Tips The interface within devices between conductors, semiconductors, and insulators is usually created by stacking patterned layers of different materials. For flexible electronics, it can be advantageous to avoid this architectural constraint. Graphene oxide, formed by chemical exfoliation of graphite, can be reduced to a more conductive form using chemical reductants. Wei et al. (p. 1373 ) now show that layers of graphene oxide can also be reduced using a hot atomic force microscope tip to create materials comparable to those of organic conductors. This process can create patterned regions (down to 12 nanometers in width) that differ in conductivity by up to four orders of magnitude.

Atomic force microscopy (AFM) has been used to assemble prototype nanostructures consisting of colloidal nanoparticles. In the standard manipulation protocol, the AFM is used either as a manipulation tool or an imaging tool, but not both at the same time. We developed a new nanomanipulation protocol in which simultaneous visual guidance is obtained during manipulation. As an example, Au nanoparticles were manipulated on a substrate in two steps. First, a nanoparticle is kicked with the z feedback off. This kicking event reduces the static friction. Second, the nanoparticle is dribbled to a target position in tapping mode, and visual guidance is provided by a ghost trace of the nanoparticle. The new manipulation protocol greatly improves efficiency of manipulating small nanoparticles (15 nm in diameter or smaller). Our work highlights the importance and challenges of understanding friction at the nanoscale.

Electric-field-induced structural transition of a single crystal $\mathrm{Pb}({\mathrm{Zn}}_{1/3}{\mathrm{Nb}}_{2/3}){\mathrm{O}}_{3}\ensuremath{-}8%{\mathrm{PbTiO}}_{3}$ grown in the (001) direction was studied by use of Raman scattering spectroscopy. By comparing the changes in Raman spectra induced by the electric field with the temperature-dependent changes, we could confirm that the structural transition to tetragonal phase is initiated at a threshold electric field ${E}_{c1}$ and completed at higher transition field ${E}_{c2}.$ In the electric-field range from ${E}_{c1}$ to ${E}_{c2},$ it is found that rhombohedral and tetragonal phases coexist. The lower threshold field ${E}_{c1}$ is found to coincide with the field at which the strain rises abruptly in the strain electric-field hysteresis loop while the upper threshold field ${E}_{c2}$ corresponds to the electric field where a slope change is observed in the high-field saturation region beyond the hysteresis loop.

An inert, precursor free, argon jet is used to control the growth rate of electron beam induced deposition. Adjustment of the jet kinetic energy/inlet temperature can selectively increase surface diffusion to greatly enhance the deposition rate or deplete the surface precursor due to impact-stimulated desorption to minimize the deposition or completely clean the surface. Physical mechanisms for this process are described. While the electron beam is also observed to generate plasma upon interaction with an argon jet, our results indicate that plasma does not substantially contribute to the enhanced deposition rate.

We report the use of thermochemical nanolithography to convert a precursor polymer film to poly(p-phenylene vinylene) with sub-100 nm spatial resolution, in ambient conditions. The local thermochemical conversion is verified by Raman spectroscopy, fluorescence imaging, and atomic force microscopy. This convenient direct writing of conjugated polymer nanostructures could be desirable for the design and fabrication of future nanoelectronic, nanophotonic, and biosensing devices.

The effects of film composition and postnitridation annealing on band gap and valence band offset were examined in nitrided Hf-silicate films prepared using direct plasma nitridation. Regardless of the composition of Hf-silicate films, the band gap characteristics were similar after direct plasma nitridation (4.5±0.1eV) and postnitridation annealing (5.6±0.1eV). The decrease in band gap after direct plasma nitridation was caused by the formation of Si–N and Hf–N bonds, while the recovery of band gap by postnitridation annealing was influenced by the dissociation of unstable Hf–N bonds. The difference in valence band offset was strongly related to the chemical states of Si–N bonds.