Two-dimensional semiconductors, such as molybdenum disulfide (MoS2), exhibit a variety of properties that could be useful in the development of novel electronic devices. However, nanopatterning metal electrodes on such atomic layers, which is typically achieved using electron beam lithography, is currently problematic, leading to non-ohmic contacts and high Schottky barriers. Here, we show that thermal scanning probe lithography can be used to pattern metal electrodes with high reproducibility, sub-10 nm resolution, and high throughput (10 5 μm 2 /h per single probe). The approach, which offers simultaneous in situ imaging and patterning, does not require a vacuum, high energy, or charged beams, in contrast to electron beam lithography. Using this technique, we pattern metal electrodes in direct contact with monolayer MoS2 for top-gate and back-gate field-effect transistors.These devices exhibit vanishing Schottky barrier heights (around 0 meV), on/off ratios of 10 10 , no hysteresis, and subthreshold swings as low as 64 mV/dec without using negative capacitors or hetero-stacks.

Gratings 1 and holograms 2 are patterned surfaces that tailor optical signals by diffraction. Despite their long history, variants with remarkable functionalities continue to be discovered 3 , 4 . Further advances could exploit Fourier optics 5 , which specifies the surface pattern that generates a desired diffracted output through its Fourier transform. To shape the optical wavefront, the ideal surface profile should contain a precise sum of sinusoidal waves, each with a well-defined amplitude, spatial frequency, and phase. However, because fabrication techniques typically yield profiles with at most a few depth levels, complex ‘wavy’ surfaces cannot be obtained, limiting the straightforward mathematical design and implementation of sophisticated diffractive optics. Here we present a simple yet powerful approach to eliminate this design–fabrication mismatch by demonstrating optical surfaces that contain an arbitrary number of specified sinusoids. We combine thermal scanning-probe lithography 6 – 8 and templating 9 to create periodic and aperiodic surface patterns with continuous depth control and subwavelength spatial resolution. Multicomponent linear gratings allow precise manipulation of electromagnetic signals through Fourier-spectrum engineering 10 . Consequently, we overcome a previous limitation in photonics by creating an ultrathin grating that simultaneously couples red, green, and blue light at the same angle of incidence. More broadly, we analytically design and accurately replicate intricate twodimensional moiré patterns 11 , 12 , quasicrystals 13 , 14 , and holograms 15 , 16 , demonstrating a variety of previously impossible diffractive surfaces. Therefore, this approach can provide benefit for optical devices (biosensors 17 , lasers 18 , 19 , metasurfaces 4 , and modulators 20 ) and emerging topics in photonics (topological structures 21 , transformation optics 22 , and valleytronics 23 ).

High-resolution lithography often involves thin resist layers which pose a challenge for pattern characterization. Direct evidence that the pattern was well-defined and can be used for device fabrication is provided if a successful pattern transfer is demonstrated. In the case of thermal scanning probe lithography (t-SPL), highest resolutions are achieved for shallow patterns. In this work, we study the transfer reliability and the achievable resolution as a function of applied temperature and force. Pattern transfer was reliable if a pattern depth of more than 3 nm was reached and the walls between the patterned lines were slightly elevated. Using this geometry as a benchmark, we studied the formation of 10–20 nm half-pitch dense lines as a function of the applied force and temperature. We found that the best pattern geometry is obtained at a heater temperature of ∼600 °C, which is below or close to the transition from mechanical indentation to thermal evaporation. At this temperature, there still is considerable plastic deformation of the resist, which leads to a reduction of the pattern depth at tight pitch and therefore limits the achievable resolution. By optimizing patterning conditions, we achieved 11 nm half-pitch dense lines in the HM8006 transfer layer and 14 nm half-pitch dense lines and L-lines in silicon. For the 14 nm half-pitch lines in silicon, we measured a line edge roughness of 2.6 nm (3σ) and a feature size of the patterned walls of 7 nm.

Applications for high resolution 3D profiles, so-called grayscale lithography, exist in diverse fields such as optics, nanofluidics and tribology. All of them require the fabrication of patterns with reliable absolute patterning depth independent of the substrate location and target materials. Here we present a complete patterning and pattern-transfer solution based on thermal scanning probe lithography (t-SPL) and dry etching. We demonstrate the fabrication of 3D profiles in silicon and silicon oxide with nanometer scale accuracy of absolute depth levels. An accuracy of less than 1nm standard deviation in t-SPL is achieved by providing an accurate physical model of the writing process to a model-based implementation of a closed-loop lithography process. For transfering the pattern to a target substrate we optimized the etch process and demonstrate linear amplification of grayscale patterns into silicon and silicon oxide with amplification ratios of ∼6 and ∼1, respectively. The performance of the entire process is demonstrated by manufacturing photonic molecules of desired interaction strength. Excellent agreement of fabricated and simulated structures has been achieved.

Thermal scanning probe lithography (t-SPL) is applied to the fabrication of chemical guiding patterns for directed self-assembly (DSA) of block copolymers (BCP). The two key steps of the overall process are the accurate patterning of a poly(phthalaldehyde) resist layer of only 3.5 nm thickness, and the subsequent oxygen-plasma functionalization of an underlying neutral poly(styrene-random-methyl methacrylate) brush layer. We demonstrate that this method allows one to obtain aligned line/space patterns of poly(styrene-block-methyl methacrylate) BCP of 18.5 and 11.7 nm half-pitch. Defect-free alignment has been demonstrated over areas of tens of square micrometres. The main advantages of t-SPL are the absence of proximity effects, which enables the realization of patterns with 10 nm resolution, and its compatibility with standard DSA methods. In the brush activation step by oxygen-plasma exposure, we observe swelling of the brush. This effect is discussed in terms of the chemical reactions occurring in the exposed areas. Our results show that t-SPL can be a suitable method for research activities in the field of DSA, in particular for low-pitch, high-χ BCP to achieve sub-10 nm line/space patterns.

The thermal radiative near field transport between vanadium dioxide and silicon oxide at submicron distances is expected to exhibit a strong dependence on the state of vanadium dioxide which undergoes a metal-insulator transition near room temperature. We report the measurement of near field thermal transport between a heated silicon oxide micro-sphere and a vanadium dioxide thin film on a titanium oxide (rutile) substrate. The temperatures of the 15 nm vanadium dioxide thin film varied to be below and above the metal-insulator-transition, and the sphere temperatures were varied in a range between 100 and 200 °C. The measurements were performed using a vacuum-based scanning thermal microscope with a cantilevered resistive thermal sensor. We observe a thermal conductivity per unit area between the sphere and the film with a distance dependence following a power law trend and a conductance contrast larger than 2 for the two different phase states of the film.

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Stabilizing and manipulating topological magnetic quasiparticles in thin films is of great interest for potential applications in data storage and information processing. Here, we present a strategy for stabilizing magnetic vortices and Bloch lines with controlled position, vorticity, and chirality in a continuous exchange bias system. By tailoring vectorially the unidirectional anisotropy of the system at the nanoscale, via thermally assisted magnetic scanning probe lithography, we show experimentally and via micromagnetic simulations the non-volatile creation of vortex-antivortex pairs. In addition, we demonstrate the deterministic stabilization of cross and circular Bloch lines within patterned Néel magnetic domain walls. This work enables the implementation of complex functionalities based on the control of tailored topological spin-textures in spintronic and magnonic nanodevices.