Scanning Probe Microscope Lithography Research Articles

Influence of Film Thickness on Nanofabrication of Graphene Oxide

Nanofabrication of two-dimensional materials through mechanical machining is normally influenced by not only process parameters such as load and velocity but also intrinsic properties such as strength and thickness. Herein, we examined the effects of graphene oxide (GO) film thickness on nanofabrication on the plane surfaces and at the step edges using scanning probe microscope lithography. The material removal of GO initiates at the load above a critical value, which strongly depends on film thickness and locations. With the increase in film thickness, the critical load decreases monotonically on the plane surfaces but increases gradually at the step edges. Further, the critical load for the GO monolayer at the step edges is at least 25 times lower than that on the plane surfaces, and the gap decreases to around 3 times when GO thickness increases to four layers. Then, mechanical nanofabrication initiating from the GO step edge allows producing various nanopatterns under extremely low loads around 1 nN. Finally, the GO nanostructures are deoxidized by annealing at 800 °C in high-purity argon to restore their highly functionalized conjugated structures, which are supported by X-ray diffraction and Raman characterizations. This work provides a novel approach to fabricating graphene-like nanostructures by deoxidizing GO after nanofabrication, which holds significant potential for applications in graphene-based devices.Graphical

Photon generator combined with silica-coated quantum dot and metamaterial fabricated by the scanning probe microscope lithography

We prototyped the solid-state photon generator composed of silica-coated quantum dot (QD) and metamaterial element using the scanning probe microscope lithography. The metamaterial element acts as an optical resonator and controls the emission of QD. For prototyping the device, QDs were trapped in a nanohole formed, and then, a metamaterial element was set around it. We succeeded in observing fine photon emission peak from the prototyped devices by the micro photoluminescence measurement. The temperature-independent wavelength of the emission peak suggested the resonance of the QD emission and the induced current in the metamaterial element.

Silica coating of PbS quantum dots and their position control using a nanohole on Si substrate

We succeeded in controlling the apparent size of a colloidal PbS quantum dot (QD) in the range of 20 to 140 nm by coating with silica and trapping the coated QDs in a nanohole prepared by scanning probe microscope lithography. Photoluminescence intensity was improved by controlling the process of adding the silica source material of tetraethoxysilane for the coating. Nanoholes of different sizes were formed on a single substrate by scanning probe oxidation with the combination of SF6 dry etching and KOH wet etching. QDs having an arbitrary energy structure can be arranged at an arbitrary position on the semiconductor substrate using this technique, which will aid in the fabrication of future nanosize solid devices such as quantum information circuits.

Controlled waveguide coupling for photon emission from colloidal PbS quantum dot using tunable microcavity made of optical polymer and silicon

A tunable microcavity device composed of optical polymer and Si with a colloidal quantum dot (QD) is proposed as a single-photon source for planar optical circuit. Cavity size is controlled by electrostatic micromachine behavior with the air bridge structure to tune timing of photon injection into optical waveguide from QD. Three-dimensional positioning of a QD in the cavity structure is available using a nanohole on Si processed by scanning probe microscope lithography. We fabricated the prototype microcavity with PbS-QD-mixed polymenthyl methacrylate on a SOI (semiconductor-on-insulator) substrate to show the tunability of cavity size as the shift of emission peak wavelength of QD ensemble.

20pm1-F4 耐摩耗プローブによるSPMリソグラフィの描画安定性向上

20pm1-F4 耐摩耗プローブによるSPMリソグラフィの描画安定性向上

Scanning Probe Microscope Lithography at the Micro- and Nano-Scales

Scanning probe microscopy (SPM)-based lithography at the micro- and nano-scales is presented. Our method in SPM local oxidation involves two SPM tips, one having a robust blunt tip, a "micrometer tip," and the other having a sharp tip, a "nanometer tip." In tapping-mode SPM local oxidation experiments, Si oxide wires with sub-10 nm resolution were produced by precisely tuning the dynamic properties of the nanometer tip such as drive amplitude and quality factor. On the other hand, in order to perform large-scale oxidation, SPM tip with a contact area of microm2, which is about 10(4) times larger than that of the conventional nanometer tip, was prepared. We propose and demonstrate a method of performing micrometer-scale SPM local oxidation using the micrometer tip under contact-mode operation. The width of the Si oxide produced was clearly determined by the contact length of the tip. Furthermore, we explore the possibility of performing the sub-20 nm lithography of Si surfaces using SPM scratching with a diamond-coated tip. The influence of various scan parameters on the groove size was investigated. The groove size could be precisely controlled by the applied force, scan direction, and the number of scan cycles. There is no effect of the scan speed on the groove size. It is concluded that high-speed nanolithography can be achieved without the degradation of patterns by SPM scratching. SPM-based lithography has the advantage of being able to fabricate a desired structure at an arbitrary position on a surface and plays an important role for bridging the gap between micro- and nano-scales.

Nanofabrication by scanning probe microscope lithography: A review

In addition to its well-known capabilities in imaging and spectroscopy, scanning probe microscopy (SPM) has recently shown great potentials for patterning of material structures in nanoscales. It has drawn the attention of not only the scientific community, but also the industry. This article examines various applications of SPM in modification, deposition, removal, and manipulation of materials for nanoscale fabrication. The SPM-based nanofabrication involves two basic technologies: scanning tunneling microscopy and atomic force microscopy. Major techniques related to these two technologies are evaluated with emphasis on their abilities, efficiencies, and reliabilities to make nanostructures. The principle and specific approach underlying each technique are presented; the differences and uniqueness among these techniques are subsequently discussed. Finally, concluding remarks are provided where the strength and weakness of the techniques studied are summarized and the scopes for technology improvement and future research are recommended.

Effect of force control algorithms on the scanning probe microscope lithography system

This letter addresses the servo issue in the scanning probe microscope (SPM) lithography. The performance of the probe controller affects the ability of the lithography system to form uniform marks on the sample surface. Different control algorithms are tested on a commercial SPM system. The tests include the controller from the original system, a proportional integral differential controller, and a modern μ controller. The design procedure for the μ controller is described. The experimental results show that carefully tuned controllers are able to suppress the undesirable vibrations, and the μ controller achieves the most uniform lithography marks.

Scanning Probe Microscope Lithography of Silicon Using a Combination of a Carbon Nanotube Tip and a Polysilane Film as a Mask

Si lithography with the line width as small as 40 nm has been demonstrated using polysilane masks prepared by scanning probe microscope lithography using a carbon nanotube tip. It has been evidenced that moisture is essential for the direct lithography of the polysilane film induced by the electron injection from the tip. The contact mode and tapping mode lithographic processes are examined for preparing the polysilane masks. It is also found that approximately 5-nm-thick polysilane films work well as a mask for a chemical etching process of Si without significant degradation.

Organized molecular assemblies for scanning probe microscope lithography

Abstract Nanostructures down to a few ten nanometers in size have been fabricated with Langmuir–Blodgett (LB) films and self-assembled monolayers (SAMs) using scanning probe microscope lithography. The SAMs have been prepared with organosilane and bipolar amphiphiles, alkanethiol molecules as ultrathin resists on Si and Au substrates. The LB films on silicon substrates using both the polymer of thiophene derivatives and the mixture of palmitic acid and hexadecylamine were prepared and fabricated. The effect of functional groups of molecules on the atomic force microscope (AFM) anodization has been studied in the optimized process conditions. Applied voltage between the AFM tip and sample, the scanning speed and the relative humidity in the laboratory are also important factors for nanometer-scale lithography of the ultrathin films. The STM lithography with an octadecanethiol SAM on Au film in the air was carried out at the pulse mode of tip bias with respect to the suitability of STM lithography. The high structural orderness and perfect thickness of ultrathin organic molecular assemblies are the major advantages as required for nanoscale lithography.

Possible application of micromachine technology for nanometer lithography

This paper describes the possible application of micromachine technology for the future nanolithography tool below 100 nm era. Due to the limitation of optical lithography in delineating sub-100 nm fine patterns, several technologies are anticipated to replace the present optical lithography. However, neither electron beam lithography nor X-ray lithography would fulfill the requirements, e.g. throughput and registration for mass production tool in the below 100 nm era. Therefore, other lithography technology has to be ready for mass production use before the year 2005∼2010. Scanning probe microscope (SPM) lithography, which uses SPM as a pattern delineation tool, would be one of the most promising candidates for the mass production tool. However, the fundamental limitations of SPM lithography in writing speed, i.e. throughput, require that the micromachine SPM technology be employed in the mass production system. A practical full wafer complex lithography system which uses 10 4∼10 6 micromachine scanning tunneling microscope (μ-STM) is proposed, and the indispensable technologies are demonstrated. It also reports on the fabrication and characterization of μ-STM using complimentary metal-oxide-semiconductor field effect transistor (CMOS FET) comptaible technologies. Finally, the observation results are presented on the vacuum tunneling gap between two conductors of the μ-STM, using a high resolution transmission electron microscope (TEM), which demonstrates the possibility of realizing a highly reliable lithography system and characterizing an atom, which would lead to an atomic resolution lithography.

Scanning probe anodization: Nanolithography using thin films of anodically oxidizable materials as resists

We report scanning probe microscope (SPM) nanolithography that uses thin films patternable by scanning probe anodization as resists. An organosilane monolayer composed of trimethylsilyl [−Si(CH3)3] groups was prepared by chemical vapor deposition on a Si substrate. It was then patterned through the localized degradation of the monolayer as a result of anodic reactions induced beneath a SPM tip. The fabricated patterns on the resist were transferred into the substrate Si by area-selective chemical etching in an aqueous NH4F/H2O2 solution. Consequently, grooves narrower than 100 nm were successfully fabricated. We have also developed another resist system for SPM lithography that is compatible with a wide range of surfaces, including insulators. The resist consisted of a thin Ti film covered with a fluoroalkylsilane monolayer. The monolayer was degraded along a tip-scanning trace. This patterned resist was etched in a dilute HF solution. The chemical etching of the underlying Ti film proceeded selectively in the region where the monolayer had been degraded, and the pattern was transferred into the Ti resist film.