Graphitic nanostripes in silicon carbide surfaces created by swift heavy ion irradiation

Abstract

The controlled creation of defects in silicon carbide represents a major challenge. A wellknown and efficient tool for defect creation in dielectric materials is the irradiation with swift (E kin Z500 keV/amu) heavy ions, which deposit a significant amount of their kinetic energy into the electronic system. However, in the case of silicon carbide, a significant defect creation by individual ions could hitherto not be achieved. Here we present experimental evidence that silicon carbide surfaces can be modified by individual swift heavy ions with an energy well below the proposed threshold if the irradiation takes place under oblique angles. Depending on the angle of incidence, these grooves can span several hundreds of nanometres. We show that our experimental data are fully compatible with the assumption that each ion induces the sublimation of silicon atoms along its trajectory, resulting in narrow graphitic grooves in the silicon carbide matrix.

Heavy Ion Induced Degradation in SiC Schottky Diodes: Incident Angle and Energy Deposition Dependence

“…Because there is no significant difference in the electric field before and after the ion strike at this location, the temperature rise can be attributed to the changes in the current density. The electron-phonon coupling can be assumed to occur at timescales of [20], [21]. This means that during the Joule heating, the temperature equilibrium between electrons and the lattice atoms is achieved faster than the timescales involved in the charge collection.…”

Response of GaN to energetic ion irradiation: conditions for ion track formation

“…The underlying material modification mechanism is different compared to classical experiments of sputtering the material by SHI in the electronic energy loss regime, when secondary ions are detected after large incidence angle irradiation, and when sputtering is assigned to vaporisation of the material [55]. In case of SiC, spatially resolved thermal spike calculations [54] indicate that surface ion tracks are formed where the temperature increase is above the required temperature for SiC decomposition. It is known that GaN undergoes decomposition via nitrogen loss when heated above 900 °C [56,57], so it is indeed very likely that a similar mechanism takes place at low stopping powers (23 MeV I 6+ ).…”

“…Ejected electrons could also promote a Coulomb explosion mechanism because charge imbalance close to the place of the SHI impact would prolong the time during which this mechanism is active. Mass removal, as observed in case of SiC [54] and GaN (Fig. 5), can also be an important channel for energy dissipation.…”

“…In a broader context, the observation of nitrogen loss reported here and the loss of silicon from the SiC surface upon SHI irradiation reported in ref. [54] opens up the question of the composition of SHI tracks. The underlying material modification mechanism is different compared to classical experiments of sputtering the material by SHI in the electronic energy loss regime, when secondary ions are detected after large incidence angle irradiation, and when sputtering is assigned to vaporisation of the material [55].…”

“…Very recently, it was shown that in case of another wide band gap material, silicon carbide (SiC), grooves with a depth of ~ 0.3 nm instead of chains of nanohillocks appear [54] when irradiated by SHI under grazing incidence angle. In a broader context, the observation of nitrogen loss reported here and the loss of silicon from the SiC surface upon SHI irradiation reported in ref.…”