[en] In this work, we introduce the use of ionoluminescence (IL) with ion beam induced secondary electron (IBISE) imaging to correlate the surface topography and crystal faces with luminescence properties. Since both IL and IBISE require low beam currents of <1 pA, simultaneous analysis can be performed. The newly installed system for light and electron detection in the NUS micro-beam facility is described. The performance of the present setup is demonstrated with high-resolution IL and IBISE images collected on Al-doped (1 1 1) c-BN and undoped (1 0 0) c-BN under 2 MeV proton irradiation. Results show that blue luminescence of Al-doped c-BN appears as triangular patterns and they tend to be associated with triangular voids on the surface. This work demonstrates the importance of combined IL and IBISE for characterizing wide band gap semiconductors

[en] The generation of secondary electrons (or δ-rays) represent a significant mode of energy loss and energy delocalisation in the penetration of a charged particle into matter. Owing to the large mass disparity between electrons and protons, (1) the trajectories of penetrating protons are essentially straight while those of electrons are tortuous and (2) the fractional energy transferred to secondary electrons by protons are much less than with electrons. Although, these suggest that protons are fundamentally capable of exhibiting superior proximity effects over electrons when used in lithography, no supporting evidence has yet been presented. In the present study we utilise the Hansen-Kocbach-Stolterfoht model for proton induced secondary electron emission to develop a Monte Carlo model capable of recreating the energy deposition profiles resulting from the creation and propagation of δ-rays produced by the passage of MeV protons in PMMA. We show that protons possess more confined energy deposition profiles than electrons

[en] The proton beam writing technique relies on a precise beam scanning and control system that offers a simple yet flexible interface for the fabrication and design of microstructures. At the Centre for Ion Beam Applications, National University of Singapore, we have developed a suite of programs, collectively known as Ionscan, that cater for the specific needs of proton beam writing. The new version of Ionscan is developed using the Microsoft Visual C++. NET development environment in conjunction with a National Instruments analog output card and NI-DAQ drivers. With the benefit of the experience gained in proton beam writing over the years, numerous enhancements and new features have been added to the scanning software since the first version of the program that was developed using LabVIEW [A.A. Bettiol, J.A. van Khan, T.C. Sum, F. Watt, Nucl. Instr. and Meth. B 181 (2001) 49]. These include the ability to perform combined stage and magnetic (or electrostatic) scanning, which is particularly useful for the fabrication of long waveguides and microfluidic channels over lengths of up to 2.5 cm. Other enhancements include the addition of the Ionutils program which gives the user the ability to design basic structures using an ASCII file format that was developed. This format contains basic information on the shape to be irradiated including the way in which it is scanned

[en] Proton beam writing has been shown to allow the fabrication of high aspect ratio nanostructures at sub-100 nm dimension and with smooth and vertical sidewalls. For applications such as the fabrication of waveguides, sidewall smoothness is an important issue. We report results from investigations into side wall roughness measured directly with Atomic Force Microscopy. Structures were written in bulk poly(methylmethacrylate) (PMMA) with 2 MeV protons specifically to allow side access. We studied the effects of different scanning algorithms and also the variation of wall roughness with development time and ion penetration depth. Our results indicate that sidewall rms roughness of less than 7 nm is readily achievable. Multi-loop scanning and optimization of the scanning algorithm can lead to significant improvements in sidewall smoothness

[en] The recent years have witnessed a proliferation of research involving proton beam (p-beam) writing. This has prompted investigations into means of optimizing the process of p-beam writing so as to make it less time consuming and more efficient. One such avenue is the improvement of the pre-writing preparatory procedures that involves beam focusing and sample alignment which is centred on acquiring images of a resolution standard or sample. The conventional mode of imaging used up to now has utilized conventional nuclear microprobe signals that are of a pulsed nature and are inherently slow. In this work, we report the new imaging system that has been introduced, which uses proton induced secondary electrons. This in conjunction with software developed in-house that uses a National Instruments DAQ card with hardware triggering, facilitates large data transfer rates enabling rapid imaging. Frame rates as much as 10 frames/s have been achieved at an imaging resolution of 512 x 512 pixels

[en] In this paper, we present a method that utilizes a focused beam of mega electron volt (MeV) protons to fabricate embedded photonic structures in Foturan^TM glass. Both direct modification via proton beam end of range damage and post irradiation heat treatment are used to make the structures. Microfluidic channels with integrated waveguides and optical diffraction gratings are made using this technique

[en] An automatic focusing system for MeV protons has been developed. The focusing system utilises rapid real time proton induced secondary electron imaging of a calibration grid coupled with a modified Gaussian fit in order to take into account the enhanced secondary electron signal from the calibration grid edge. The focusing system has been successfully applied to MeV protons focused using a coupled triplet configuration of magnetic quadrupole lenses (Oxford triplet). Automatic beam focusing of a coarse beamspot of approximately (5 x 3.5) micrometres in the X and Y directions to a sub-micrometre beamspot of approximately (0.7 x 0.6) micrometers was achieved at a beam current of about 50 pA