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Register a new userFabrication of InP nano pillars by ECR Ar ion irradiation
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Regular arrays of InP nano pillars have been fabricated by low energy Electron Cyclotron Resonance (ECR) Ar+ ion irradiation on InP(111) surface. Several scanning electron microscopy (SEM) images have been utilized to invetsigate the width, height, and orientation of these nano pillars on InP(111) surfaces. The average width and length of these nano-pillars are about 50 nm and 500 nm, respectively. The standing angle with respect to the surface of the nano-pillars depend on the incidence angle of the Ar ion irradiation during the fabrication process. Interestingly, the growth direction of the nano pillars are along the reflection direction of the ion beam and the standing angles are nearly same as the ion incidence angle with the surface normal. This nano-pillas are easily transferred from the InP surface to double sided carbon tape without any damage. High Resolution Transmission Electron Microscopy (HRTEM) study of single nano-pillar reveals that this nano-pillar are almost crystalline in nature except 2-4 nm amorphous layer on the outer surface. The transmission electron microscopy combined with energy-dispersive x-ray spectroscopy (TEM-EDS) analysis of these nano pillars exhibit that the ratio of In and P is little higher compared to the bulk InP.
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We report formation of self organized InP nano dots using 3 keV Ar+ ion sputtering, at $15^circ$ incidence from surface normal, on InP(111) surface. Morphology and optical properties of the sputtered surface, as a function of sputtering time, have been investigated by Scanning Probe Microscopy and Raman Scattering techniques. Uniform patterns of nano dots are observed for different durations of sputtering. The sizes and the heights of these nano dots vary between 10 to 100 nm and 20 to 40 nm, respectively. With increasing of sputtering time, t, the size and height of these nano dots increases up to a certain sputtering time $t_c$. However beyond $t_c$, the dots break down into smaller nanostructures, and as a result, the size and height of these nanostructures decrease. The uniformity and regularity of these structures are also lost for sputtering beyond $t_c$. The crossover behavior is also observed in the rms surface roughness. Raman investigations of InP nano dots reveal optical phonon softening due to phonon confinement in the surface nano dots.
This paper presents experimental data and analysis of the structural damage caused by swift-heavy ion irradiation of single-crystal diamond. The patterned buried structural damage is shown to generate, via swelling, a mirror-pattern on the sample surface, which remains largely damage-free. While extensive results are available for light ion implantations, this effect is reported here for the first time in the heavy ion regime, where a completely different range of input parameters (in terms of ion species, energy, stopping power, etc.) is available for customized irradiation. The chosen ion species are Au and Br, in the energy range 10-40 MeV. The observed patterns, as characterized by profilometry and atomic force microscopy, are reported in a series of model experiments, which show swelling patterns ranging from a few nm to above 200 nm. Moreover, a systematic phenomenological modelling is presented, in which surface swelling measurements are correlated to buried crystal damage. A comparison is made with data for light ion implantations, showing good compatibility with the proposed models. The modelling presented in this work can be useful for the design and realization of micropatterned surfaces in single crystal diamond, allowing to generate highly customized structures by combining appropriately chosen irradiation parameters and masks.
Many of the proposed future applications of graphene require the controlled introduction of defects into its perfect lattice. Energetic ions provide one way of achieving this challenging goal. Single heavy ions with kinetic energies in the 100 MeV range will produce nanometer-sized defects on dielectric but generally not on crystalline metal surfaces. In a metal the ion-induced electronic excitations are efficiently dissipated by the conduction electrons before the transfer of energy to the lattice atoms sets in. Therefore, graphene is not expected to be irradiation sensitive beyond the creation of point defects. Here we show that graphene on a dielectric substrate sustains major modifications if irradiated under oblique angles. Due to a combination of defect creation in the graphene layer and hillock creation in the substrate, graphene is split and folded along the ion track yielding double layer nanoribbons. Our results indicate that the radiation hardness of graphene devices is questionable but also open up a new way of introducing extended low-dimensional defects in a controlled way.
We show that the work function of exfoliated single layer graphene can be modified by irradiation with swift (E_{kin}=92 MeV) heavy ions under glancing angles of incidence. Upon ion impact individual surface tracks are created in graphene on SiC. Due to the very localized energy deposition characteristic for ions in this energy range, the surface area which is structurally altered is limited to ~ 0.01 mum^2 per track. Kelvin probe force microscopy reveals that those surface tracks consist of electronically modified material and that a few tracks suffice to shift the surface potential of the whole single layer flake by ~ 400 meV. Thus, the irradiation turns the initially n-doped graphene into p-doped graphene with a hole density of 8.5 x 10^{12} holes/cm^2. This doping effect persists even after heating the irradiated samples to 500{deg}C. Therefore, this charge transfer is not due to adsorbates but must instead be attributed to implanted atoms. The method presented here opens up a new way to efficiently manipulate the charge carrier concentration of graphene.
As impermeable to gas molecules and at the same time transparent to high-energy ions, graphene has been suggested as a window material for separating a high-vacuum ion beam system from targets kept at ambient conditions. However, accumulation of irradiation-induced damage in the graphene membrane may give rise to its mechanical failure. Using atomistic simulations, we demonstrate that irradiated graphene even with a high vacancy concentration does not show signs of such instability, indicating a considerable robustness of graphene windows. We further show that upper and lower estimates for the irradiation damage in graphene can be set using a simple model.
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