S. Deladi

Micromachined fountain pen for atomic force microscope-based nanopatterning

We present a tool that can be used in standard atomic force microscope and that enables chemical, chemical/mechanical, or physical surface modification using continuous liquid supply. The device consists of a reservoir micromachined into the probe support that is connected to fluidic channels embedded in a V-shaped cantilever. Via the fluidic channels, the liquid reaches the tip. The fluid transport to the sample surface is demonstrated and fountain pen lithography applications are presented.

Monolithic fiber-top sensor for critical environments and standard applications

We present a monolithic device obtained by carving a cantilever on the top of a single-mode optical fiber. We show that the vertical position of the cantilever can be determined with accuracy comparable to atomic force microscopes and other commonly used scientific instruments. The device does not require any alignment procedure and can be used in critical environments as well as in standard applications.

Fabrication of micromachined fountain pen with in situ characterization possibility of nanoscale surface modification

We present the fabrication process of a tool that can be used in standard atomic force microscope (AFM) for in situ characterization of chemical, chemical?mechanical or physical surface modification performed with the same device. The image obtained during scanning contains information about the modified and unmodified topographies for each scanning line, thus quantification of surface topography modification (e.g. wear, deposition) or the change of different parameters (e.g. friction force) can be followed as it occurs. The device allows continuous fluid supply for different localized applications. The reservoir, micromachined into the AFM probe support, is connected to fluidic channels embedded in a V-shaped cantilever. Via the fluidic channels the liquid reaches the tip, where surface modification occurs. With a second cantilever, used only for measurement, the surface modification is characterized in situ. Due to multiple functionality of the device the applications range from nanoscale tribological studies (lubricated and dry conditions) to lithography (deposition, etching).

Carving fiber-top optomechanical transducers from an optical fiber

In a recent paper (Iannuzzi et al 2006 Monolithic fiber-top sensor for critical environments and standard applications Appl. Phys. Lett. 88 053501) we have presented the principle of the fiber-top position sensor, having a monolytical structure carved out of a single-mode optical fiber. The device alleviates sensing in a critical environment via interferometric readout, and because of its monolithic construction, facilitates plug-and-play utilization without alignment. In this paper we describe the fabrication method of a similar device which, however, was also equipped with a pyramidal tip on the top of the cantilever, an important detail for future implementation in scanning probe microscopy. A silicon surface was then periodically put in contact and moved out of contact with the device. The output signal resembles force curves that can be similarly obtained with atomic force microscopes.

Fiber-top atomic force microscope

We present the implementation of an atomic force microscope (AFM) based on fiber-top design. Our results demonstrate that the performances of fiber-top AFMs in contact mode are comparable to those of similar commercially available instruments. Our device thus represents an interesting alternative to existing AFMs, particularly for applications outside specialized research laboratories, where a compact, user-friendly, and versatile tool might often be preferred.

Flash-release - an alternative for releasing complex MEMS devices

A novel time-saving and cost-effective release technique has been developed and is described. The physical nature of the process is explained in combination with experimental observations. The results of the flash release process are compared with those of freeze-drying and supercritical CO2 releasing. It is demonstrated that the new technique is not only simpler but it also gives better yield for long cantilevers. Furthermore, it is shown that the process can be used successfully for complex MEMS devices that consist of multiple-structural layers, but which do not contain membrane-like structures.

Innovative process development for a new micro-tribosensor using surface micromachining

We present a study on thick Si-rich nitride/polycrystalline Si/silicon oxide multilayer-stacks made by LPCVD and PECVD techniques. The pattern transfer into the multilayer-stacks is achieved by dry etching techniques such as SF6-based ICP plasma and the so-called Bosch processes. The steep profiles and high selectivity obtained for the developed processes allow us to design and fabricate complex MEMS devices which consist of multiple sacrificial and multiple locally doped Si or polycrystalline Si layers. A new etch-stop technique has been developed, which allows accurate stopping on any particular layer with the SF6-based ICP plasma etch process. In order to obtain freestanding structures for tribotesting purposes, the residual stress variation of thick undoped silicon oxide layers (obtained by various methods) has been studied for high temperature processing.

In situ characterization technique for nanotribological investigations

An innovative technique has been developed to enable in situ monitoring of mechanical surface modification. The method is based on using a test surface and a sharp tip located on two different cantilevers; one for mechanical surface modification and the other for in situ detection of surface topography change. The device can be used in standard atomic force microscope, the image obtained during scanning contains information about a partly modified and a partly unmodified topography for each scanning line, thus quantification of surface topography modification (e.g., wear) or the change of different parameters (e.g., friction force) can be followed as it occurs. The characterization technique and typical results are presented.

Parallel-beams/lever electrothermal out-of-plane actuator

We report on the design, modeling, fabrication and testing of a new electrothermal actuator allowing for various modes of movement and exhibiting large enough forces to be usable in a micro-tribotester. The performance of the actuator has been simulated combining numerical and analytical calculations. Experiments have been performed in ambient conditions and vacuum. The theoretical results and measurements are consistent if the temperature dependence of the properties of the polycrystalline Si is taken into account.

Distinction of the irreversible and reversible actuation regions of b-doped poly-si based electrothermal actuators

Polycrystalline-Si microactuators based on electrothermal principles exhibit many interesting features but their practical use is severely limited by permanent damage that may occur due to accidental overheating. Under these conditions, polycrystalline-Si structures will display irreversible structural changes ranging from slight geometrical deformations to complete damage. In this paper, an approach is presented to avoid permanent structural deformation of B-doped polycrystalline-Si based electrothermal actuators by overheating. The method allows us to distinguish reversible and irreversible actuation conditions and is demonstrated under environmental and vacuum conditions. It enables full utilization of the capabilities of B-doped polycrystalline-Si based electrothermal actuators with reproducible performance.