Malte Bartenwerfer

Nanorobotic Assembly and Focused Ion Beam Processing of Nanotube-Enhanced AFM Probes

In this paper, a focused ion beam processing technique is presented that facilitates the modification of carbon nanotubes (CNTs) in terms of length, diameter, and orientation. The CNTs are mounted onto an atomic force microscope (AFM) probe by using a nanorobotic microgripper-based pick-and-place handling strategy. Such CNT-enhanced AFM probes are needed for metrology measurements of nanostructures with critical dimensions and high aspect ratios. The complete process of assembly and processing is realized inside a nanorobotic dual beam scanning electron microscope (SEM) and focused ion beam (FIB) machine.

In situ SEM electromechanical characterization of nanowire using an electrostatic tensile device

This paper presents a method for simultaneously performing mechanical tensile test and electrical test on nanowire in SEM. For this purpose, an electrostatic tensile device is designed, fabricated and tested. In order to simplified the testing system, microforce sensor beam is used to measure the tensile force applied to the nanowire instead of traditional capacitive force sensor. Special care is taken on the design and fabrication process to improve the resolution of mechanical measurement by SEM imaging. Mechanical properties such as Youngs modulus, elastic limit and fracture strength, and electrical resistance of nanowire can be obtained in the process of tensile testing using this device. Cu nanowire and SiC nanowire are tested as examples in this paper. Smaller Youngs modulus is found in both nanowires due to the imperfection in crystallization. On the other hand, electrical properties under different tensile stress are characterized for both nanowires. Nonlinear and identical I–V curves are revealed for Cu nanowire, and linear I–V curves and the piezoresistive effect are revealed for SiC nanowire. The gauge factor of SiC nanowire is calculated and turns out to be compatible with the values of bulk SiC published in the literature.

Automated handling and assembly of customizable AFM-tips

Todays processes in micro- and nanofabrication include several critical dimension metrology steps to guarantee device performance. Especially in the manufacturing process of novel disruptive photonic devices and nanoelectronic circuit architectures, new 3D acquisition and visualization techniques for metrology are required. Two of the most important parameters are the line width and sidewall roughness of vertical interconnects and nanooptical structures. The measurement of these parameters becomes increasingly challenging as the continuous shrinking of dimensions requires higher lateral resolution. The AFM has become a standard and widely spread instrument for characterizing such nanoscale devices and can be found in most of todays research and development areas. However, the characterization of three dimensional high-aspect ratio and sidewall structures is still a bottleneck. Novel exchangeable and customizable scanning probe tips, so-called NanoBits, can be attached to standard AFM cantilevers offering unprecedented freedom in adapting the shape and size of the tips to the surface topology of the specific application. In order to realize the in-situ exchange of NanoBits within the AFM environment the NanoBits have to be provided in a freestanding way that allows the AFM cantilever to be aligned and connected to the NanoBits. Due to the fact that direct microfabrication of such structures is still challenging, a nanorobotic preassembly of NanoBits cartridges is reasonable. These cartridges are intended to contain several NanoBits with a variety of different tip-shapes.

Automated robotic assembly for a micro-cartridge system inside the scanning electron microscope.

The AFM is a common tool for ultra-precise surface characterization and a standard instrument a variety of research and development disciplines. However, the characterization of three dimensional high-aspect ratio and sidewall structures remains a hardly accomplishable task. Novel exchangeable and customizable scanning probe tips - NanoBits - can be attached to standard AFM cantilevers offering unprecedented freedom in adapting the shape and size of the tips. These NanoBits of few μm size have to be assembled into micro-cartridges. This challenging assembly task is performed inside the SEM by a micro-gripper. A powerful automation framework has been developed facilitating image based automation and visual servoing for this task. Template matching, BLOB-detection, and special SEM-based detection approaches are used to achieve the automated assembly.

Directed nanorobot-based handling of single nanowires

Within this paper, a new experimental implementation is presented in order to facilitate well directed handling of silicon nanowires with dimensions of about 10 μm length and less than 100 nm diameter. The experimental strategy employs adhesive bond techniques and FIB assisted milling to transfer nanowires from a production substrate to a different electrode substrate for electrical characterization. Thus, further electrical characterization measurements were achieved, which are important for future applications of nanowires. An accurate picking from high-dense nanowire forests, a transfer over several centimeters, and a well directed placement onto the target are feasible using the presented handling technique. This contribution explains advantages, prospects and limits of the proposed handling strategy with regard to an automation heading for future applications.

Towards automated AFM-based nanomanipulation in a combined nanorobotic AFM/HRSEM/FIB system

In this paper, the semi-automated AFM-based nanomanipulation of silica spheres with a radius of 550 nm is presented. A combined AFM/HRSEM/FIB system is used to facilitate the SEM vision-based pick-and-place handling with haptic feedback. Object recognition and tracking algorithms are described supporting the automated localization of micro-and nanospheres. Automated alignment of source and target sample positions is realized to support fast exchange of different substrates and to speed up the pick-and-place procedure. The integration of a haptic feedback device allows for intuitive AFM-based nanomanipulation with force feedback. The silica spheres are assembled into 2×2 μm arrays for applications in infrared spectroscopy.

Tracking algorithms for closed-loop positioning of mobile microrobots

Visual servoing of tools and object detection are major tasks of serial micro-assembly, as the visual feedback is often the only way to track positions. High speed cameras can be used for high speed automated micromanipulation. This paper analyzes different object tracking approaches for their feasibility of high speed tracking. First, state of the art software algorithms are analyzed. Second, a hardware approach is analyzed. All algorithms are compared in terms of high-speed feasibility, movement speed and limitations. The comparison shows that hardware-based approaches are needed for update frequencies beyond 100 Hz.

Individual nanowire handling for NEMS fabrication

This paper presents the development of a novel technique for well directed handling of nanowires made of different materials with diameters down to 100nm or less and length up to several ten μms. The presented transfer technique uses an adhesive bond handling approach and is able to bridge any distance between the nanowires source and target. The operational range is only limited by the robotic setup, which is mounted inside a high-resolution scanning electron microscope. Additionally, focused ion beam and gas injection systems are used. This transfer approach is a seminal technique towards an assembly of nanowire based devices.

Automated handling of bio-nanowires for nanopackaging

The integration of biomaterials into micro/nano-sensors or micro/nano-systems is expected to improve the properties of such systems or even lead to the development of novel innovative systems. A key problem to be solved beforehand is the development and realization of proper preparation, handling and manipulation methods with respect to an industrial usage. To enable such a usage, the methods have to be automatable, robust to environmental changes as well as feasible in a scanning electron microscope (SEM). According to these points, the target of the presented efforts is to develop these methods for a future design of nanoelectronic parts and to solve packaging problems at the nanoscale. As a consequence, the paper presents a novel concept for the usage of biomaterials, such as DNA and wood fibers/fibrils, for the packaging at the nanoscale. Novel methods for the DNA-handling with an atomic force microscope (AFM) at dry conditions, which can also be used in the vacuum chamber of a SEM will be presented as well as wood fibers/fibrils manipulation methods in the SEM.

Nanomaterials Enter the Silicon-Based CMOS Era: Nanorobotic Technologies for Nanoelectronic Devices.

This article focuses on nanomaterials referring to structures with nanometer sizes in at least one dimension: monolayered sheets of carbon, so-called graphene, is the best-known example for two-dimensional nanostructures, while nanotubes and nanowires made of different materials, such as Ag, Au, BN, C, Si, TiO2, and ZnO, are fascinating one-dimensional structures in which carbon nanotubes (CNTs) are the most prominent example.