Mechanism and development of dip-pen nanolithography(DPN)

Dip-pen nanolithography is a new scanning probe lithography (SPL) technique based on atomic force microscopy (AFM), and now has made a great progress. The process of dip-pen lithography involves the adsorption of ink molecules on AFM tip, the formation of water meniscus, the transport of ink molecules, and diffusion of ink molecules on the substrate. More factors such as temperature, humidity, tip, scanning speed and so on will influence the process of dip-pen lithography. The paper analyzes in detail the mechanism of this technique, introduces synthetically the latest development, including electrochemical DPN, more-mode DPN, multiple DPN, multi-probe array DPN and so on. Finally, the paper describes the characteristics and the application of DPN.

Non-alkyl tin-oxo clusters as new-type patterning materials for nanolithography

Nanolithography plays crucial roles in the miniaturization of dense integrated circuit,which extremely depends on innovative resist materials.Recently,metal-containing resists have been explored due to their higher short-wavelength photon absorption than traditional polymer resists.Herein,for the first time,the patterning performance of non-alkyl tin-oxo clusters has been evaluated.Meanwhile,the influence of structural characteristics on resolution and sensitivity has been investigated.To evaluate the surface ligand effect,three non-alkyl Sn_(10)-oxo clusters with the same core were functionalized with pyrazole,3-methylpyrazole and 4-methylpyrazole,respectively.Furthermore,another Sn_(14)-oxo cluster with similar core configuration was also prepared using 4-methylpyrazole ligand to study the influence of Sn nuclearity.Spin-coating method was then applied to fabricate thin films of these non-alkyl tin-oxo clusters on Si substrate,which showed various thicknesses and roughnesses.More interestingly,electron beam lithography(EBL)patterning studies indicated that for the same Sn_(10)core,the 4-methylpyrazoledecorated clusters showed the best performance.As for the different cluster cores with the same 4-methylpyrazole ligand,the patterns of Sn_(10)with the higher ligand:Sn ratio are also better than those of Sn_(14).Finally,distinguishable 50 nm resolution was achieved by 4-methylpyrazole-decorated Sn_(10)at expose energy of 100μC/cm2which can be significantly improved by increasing expose energy to 1,000μC/cm2as confirmed by atomic force microscopy(AFM)images.This work not only opens the nanolithography applications of non-alkyl tin-oxo clusters,but also provides an effective structural methodology for improving their patterning performance in future.

Self-aligned fiber-based dual-beam source for STED nanolithography

A fiber-based source that can be exploited in a stimulated emission depletion(STED) inspired nanolithography setup is presented.Such a source maintains the excitation beam pulse, generates a ring-shaped depletion beam, and automatically realizes dual-beam coaxial alignment that is critical for two beam nanolithography.The mode conversion of the depletion beam is realized by using a customized vortex fiber, which converts the Gaussian beam into a donut-shaped azimuthally polarized beam.The pulse width and repetition frequency of the excitation beam remain unchanged, and its polarization states can be controlled.According to the simulated point spread function of each beam in the focal region, the full width at half-maximum of the effective spot size in STED nanofabrication could decrease to less than 28.6 nm.

Material transport in dip-pen nanolithography

Dip-pen na.nolithography （DPN） is a useful method for directly printing materials on surfaces with sub-50nm resolution. Because it, involves the physical transport of materials from a scanning probe tip to a surface and the subsequent chemical interaction of that material with the surface, there are many factors to consider when attempting to understand DPN. In this review, we overview the physical and chemical processes that are known to play a role in DPN, Through a detailed review of the literature, we classify inks into three general categories based on their transport properties, and highlight the myriad ways that. DPN can be used to perform chemistry at the tip of a scanning probe.

Study on electrothermally actuated cantilever array for nanolithography

Nanolithography is a patterning technique for the fabrication of nano-scale structures.A promising method of nanolithography known as scanning probe lithography has particularly extensive applications for its high resolution,high reliability,and simple operation.In this paper,a novel electrothermally actuated cantilever with integrated heater,thermal conductor and actuator for scanning probe lithography is proposed.Cantilevers are designed in an 8×4 array.Analytical models are presented to simulate the temperature distribution,deflection and thermal crosstalk of the cantilever array.This structure is successfully fabricated.It is demonstrated that this structure can produce a tip deflection of 16.9 μm at an actuation current of 5.5 mA and the thermal crosstalk between the cantilevers is neglected.

High-fidelity transfer of area-selective atomic layer deposition grown HfO_(2)through DNA origami-assisted nanolithography

DNA origami-assisted nanolithography(DOANL)for fabricating custom-designed nanomaterials through pattern transfer from DNA origami to different substrates materials are presented.However,the pattern's integrity and resolution face considerable challenges due to the uncontrollable growth of the nanomaterials during transformation and the unclear mechanism of DOANL.Herein,we report a DOANL combined with area-selective atomic layer deposition(ALD)strategy for fabricating custom shapes hafnium oxide(HfO2)with the high-fidelity and high-throughput.We find that the HfO_(2)selectively grows on DNA origami substrates in a hydroxyl-rich area instead of a methyl-rich protective layer.Combined with the merit of the area-selective ALD method,theHfO_(2)atom selectively coated on the DNA origami surface,thus,precisely modeling the shapes with high-precision in our study based on the surface groups difference of DNA origami and the naked hexamethyldisilane(HMDS)-treated substrates,which reveal the mechanical of high-fidelity pattern transfer based on DOANL.As a result,DNA origami structures can program the shape ofHfO_(2)nanostructures.The DOANL that is based on the principle of"bottom-up"precision assembly breaks through the shape complexity and high-throughput fabrication limitation of theHfO_(2)nanostructures,including two-and three-dimensional structures,plane and curved structures,monolithic and hollow structures.Based on the"top-down"accurate fabrication principle,the area-selective ALD on methyl-rich protective layer substrates improves the integrity and resolution of the pattern transfer process.Overall,this work provides a general technology for nanofabrication strategy.

Dip-Pen Nanolithography(DPN): from Micro/Nano-patterns to Biosensing

Dip-pen nanolithography is an emerging and attractive surface modification technique that has the capacity to directly and controllably write micro/nano-array patterns on diverse substrates.The superior throughput,resolution,and registration enable DPN an outstanding candidate for biological detection from the molecular level to the cellular level.Herein,we overview the technological evolution of DPN in terms of its advanced derivatives and DPN-enabled versatile sensing patterns featuring multiple compositions and structures for biosensing.Benefitting from uniform,reproducible,and large-area array patterns,DPN-based biosensors have shown high sensitivity,excellent selectivity,and fast response in target analyte detection and specific cellular recognition.We anticipate that DPN-based technologies could offer great potential opportunities to fabricate multiplexed,programmable,and commercial array-based sensing biochips.

3D printed fiber-optic nanomechanical bioprobe

Ultrasensitive nanomechanical instruments,e.g.atomic force microscopy(AFM),can be used to perform delicate biomechanical measurements and reveal the complex mechanical environment of biological processes.However,these instruments are limited because of their size and complex feedback system.In this study,we demonstrate a miniature fiber optical nanomechanical probe(FONP)that can be used to detect the mechanical properties of single cells and in vivo tissue measurements.A FONP that can operate in air and in liquids was developed by programming a microcantilever probe on the end face of a single-mode fiber using femtosecond laser two-photon polymerization nanolithography.To realize stiffness matching of the FONP and sample,a strategy of customizing the microcantilever’s spring constant according to the sample was proposed based on structure-correlated mechanics.As a proof-of concept,three FONPs with spring constants varying from 0.421 N m^(−1)to 52.6 N m^(−1)by more than two orders of magnitude were prepared.The highest microforce sensitivity was 54.5 nmμN^(−1)and the detection limit was 2.1 nN.The Young’s modulus of heterogeneous soft materials,such as polydimethylsiloxane,muscle tissue of living mice,onion cells,and MCF-7 cells,were successfully measured,which validating the broad applicability of this method.Our strategy provides a universal protocol for directly programming fiber-optic AFMs.Moreover,this method has no special requirements for the size and shape of living biological samples,which is infeasible when using commercial AFMs.FONP has made substantial progress in realizing basic biological discoveries,which may create new biomedical applications that cannot be realized by current AFMs.

Sub-10 nm fabrication:methods and applications

Reliable fabrication of micro/nanostructures with sub-10 nm features is of great significance for advancing nanoscience and nanotechnology.While the capability of current complementary metal-oxide semiconductor(CMOS)chip manufacturing can produce structures on the sub-10 nm scale,many emerging applications,such as nano-optics,biosensing,and quantum devices,also require ultrasmall features down to single digital nanometers.In these emerging applications,CMOS-based manufacturing methods are currently not feasible or appropriate due to the considerations of usage cost,material compatibility,and exotic features.Therefore,several specific methods have been developed in the past decades for different applications.In this review,we attempt to give a systematic summary on sub-10 nm fabrication methods and their related applications.In the first and second parts,we give a brief introduction of the background of this research topic and explain why sub-10 nm fabrication is interesting from both scientific and technological perspectives.In the third part,we comprehensively summarize the fabrication methods and classify them into three main approaches,including lithographic,mechanics-enabled,and post-trimming processes.The fourth part discusses the applications of these processes in quantum devices,nano-optics,and high-performance sensing.Finally,a perspective is given to discuss the challenges and opportunities associated with this research topic.

Effects Associated with Nanostructure Fabrication Using In Situ Liquid Cell TEM Technology

We studied silicon,carbon,and SiC xnanostructures fabricated using liquid-phase electron-beam-induced deposition technology in transmission electron microscopy systems.Nanodots obtained from fixed electron beam irradiation followed a universal size versus beam dose trend,with precursor concentrations from pure Si Cl4to 0%SiC l4in CH2Cl2,and electron beam intensity ranges of two orders of magnitude,showing good controllability of the deposition.Secondary electrons contributed to the determination of the lateral sizes of the nanostructures,while the primary beam appeared to have an effect in reducing the vertical growth rate.These results can be used to generate donut-shaped nanostructures.Using a scanning electron beam,line structures with both branched and unbranched morphologies were also obtained.The liquid-phase electron-beaminduced deposition technology is shown to be an effective tool for advanced nanostructured material generation.

Applications of optically and electrically driven nanoscale bowtie antennas

Optical antennas play an important role in optical field manipulation.Among them,nanoscale bowtie antennas have been extensively studied for its high confinement and enhancement.In this mini-review,we start with a brief introduction of bowtie antennas and underlying physics.Then we review the applications with respect to optically and electrically excited nanoscale bowtie antennas.Optically driven bowtie antennas enable a set of optical applications such as near-field imaging/trapping,nonlinear response,nanolithography,photon generation and detection.Finally,we put emphasis on the principle and applications of electrically driven bowtie antennas,an emerging method of generating ultrafast and broadband tunable nanosources.In a word,nanoscale bowtie antennas still have great potential research value to explore.

A functional probe with bowtie aperture and bull's eye structure for nanolithograph

The bowtie aperture surrounded by concentric gratings(the bull’s eye structure) integrated on the near-field scanning optical microscopy(NSOM) probe(aluminum coated fiber tip) for nanolithography has been investigated using the finite-difference time domain(FDTD) method.By modifying the parameters of the bowtie aperture and the concentric gratings,a maximal field enhancement factor of 391.69 has been achieved,which is 18 times larger than that obtained from the single bowtie aperture.Additionally,the light spot depends on the gap size of the bowtie aperture and can be confined to sub-wavelength.The superiority of the combination of the bowtie aperture and the bull’s eye structure is confirmed,and the mechanism for the electric field enhancement in this derived structure is analyzed.

Alkenyl-type ligands functionalized tin-lanthanide oxo nanoclusters as molecular lithography resists

Both the cluster chemistry of tin and lanthanides have attracted extensive research interest,showing wide applications in catalysis,magnetism,luminescence,and lithography.However,their fusion into heterometallic Sn-Ln oxo clusters is still to be explored.In this study,through the stabilization of alkenyl-type cis-5-norbornene-endo-2,3-dicarboxylic acid(H_(2)NE)ligands,a series of atomically precise Sn-Ln oxo nanoclusters have been successfully constructed from the assembly of heterometallic tetranuclear Sn_(x)Ln((4-x))building blocks.Thereinto,Sn_(12)Eu_(8) and Sn_(13)Er_(6) with the highest nuclearities are built from multiple assembly of 8{Sn_(2)Eu_(2)}units and 6{Sn_(3)Er}and{Sn_(2)Er_(2)}units,respectively.ESI-MS analysis indicates that Sn_(13)Er_(6) has high solution stability,allowing their packing into thin films for lithography applications.As a result of electron beam lithography(EBL)studies,the condensation of Sn_(13)Er_(6) can be triggered by low energy radiation of 10μC/cm^(2),and 50 nm lines have been fabricated at expose energy of 50μC/cm^(2),confirming the satisfying sensitivity and resolution of Sn_(13)Er_(6).Hence,the success of this study develops the chemistry of heterometallic tin-lanthanide clusters that can be applied as novel negative photoresist materials.

SANTA： Self-aligned nanotrench ablation via Joule heating for probing sub-20 nm devices

Manipulating materials at the nanometer scale is challenging, particularly if alignment with nanoscale electrodes is desired. Here, we describe a lithography-free, self-aligned nanotrench ablation （SANTA） technique to create nanoscale ＂trenches＂ in a polymer like poly（methyl methacrylate） （PMMA）. The nanotrenches are self-aligned with carbon nanotube （CNT） or graphene ribbon electrodes through a simple Joule heating process. Using simulations and experiments we investigated how the Joule power, ambient temperature, PMMA thickness, and substrate properties affect the spatial resolution of this technique. We achieved sub-20 nm nanotrenches, for the first time, by lowering the ambient temperature and reducing the PMMA thickness. We also demonstrated a functioning nanoscale resistive memory （RRAM） bit self- aligned with a CNT control device, achieved through the SANTA approach. This technique provides an elegant and inexpensive method to probe nanoscale devices using self-aligned electrodes, without the use of conventional alignment or lithography steps.

Wafer scale direct-write of Ge and Si nanostructures with conducting stamps and a modified mask aligner

The broad availability of high throughput nanostructure fabrication is essential for advancement in nanoscale science. Large-scale manufacturing developed by the semiconductor industry is often too resource-intensive for medium scale laboratory prototyping. We demonstrate the inexpensive wafer scale direct- write of Ge and Si nanostructures with a 4-inch mask aligner retrofitted with a conducting microstructured stamp. A bias applied between the stamp and an underlying silicon substrate results in the reaction of diphenylgermane and diphenylsilane precursors at the stamp--substrate interface to yield the direct- write of Ge and Si nanostructures in determined locations. With the increasing number of outdated mask aligners available from the semiconductor industry and an extensive library of liquid precursors, this strategy provides facile, inexpensive, wafer scale semiconductor direct-write for applications such as electronics, photonics, and photovoltaics.

Micro- and Nanostripes of Self-Assembled Au Nanocrystal Superlattices by Direct Micromolding

A simple,inexpensive direct micromolding method for patterning Au nanocrystal superlattices using a polydimethylsiloxane(PDMS)stamp has been developed.The method involves in situ synthesis of Au(I)dodecanethiolate and its decomposition leading to Au nanocrystals in the microchannels of the stamp which order themselves to form patterned superlattice stripes,in conformity with the stamp geometry.Owing to its insolubility in common solvents,the dodecanethiolate was made by reacting Au(PPh3)Cl and dodecanethiol in situ inside the microchannels,by injecting first the former solution in toluene at room temperature followed by the thiol solution at 120°C.Annealing the reaction mixture at 250°C,resulted in formation of nanocrystals(with a mean diameter of 7.5 nm)and hexagonal ordering.By using an external pressure while molding,parallel stripes with sub-100 nm widths were obtained.The choice of parameters such as injection temperature of the thiol and concentrations is shown to be important if an ordered superlattice is to be obtained.In addition,these parameters can be varied as a means to control the nanocrystal size.

A Study of Electron Beam Induced Deposition and Nano Device Fabrication Using Liquid Cell TEM Technology

SiCx nano dots and nano wires with sizes from 60 nm to approximately 2μm were fabricated using liquid cell transmission electron microscope(TEM)technology.A SiCl_(4)in CH_(2)Cl_(2)solution was sealed between two pieces of Si_(3)N_(4)window grids in an in situ TEM liquid cell.Focused 200 keV electron beams were used to bombard the sealed precursors,which caused decomposition of the precursor materials,and deposition of the nano materials on the Si_(3)N_(4)window substrates.The size of nano dots increased with beam exposure time,following an approximately exponential relationship with the beam doses.Secondary electrons are attributed as the primary sources for the Si and C reduction.A nano device was formed from a deposited nano wire,with its electrical property characterized.

Highly sensitive gas sensors on low-cost nanostructured polymer substrates

SnO_(2)thin-film gas sensors have been successfully fabricated on nanospiked polyurethane polymer surfaces,which are replicated by a low-cost soft nanolithography method from silicon nanospike structures formed with femtosecond laser irradiations.Measurements revealed significant response to carbon monoxide(CO)gas at room temperature,which is considerably different from the sensors of SnO_(2)thin films coated on smooth surfaces that show no response to CO gas at room temperature.The high area/volume ratio and sharp structures of the nanospikes enhance the sensitivity of SnO_(2)at room temperature.This will greatly decrease the electrical power consumption of the gas sensor and the cost for calibrations,and has great potential for application in other sensing systems.