Direct fabrication of three-dimensional buried conductive channels in single crystal diamond with ion microbeam induced graphitization

Abstract

We report on a novel method for the fabrication of three-dimensional buried graphitic micropaths in single crystal diamond with the employment of focused MeV ions. The use of implantation masks with graded thickness at the sub-micrometer scale allows the formation of conductive channels which are embedded in the insulating matrix at controllable depths. In particular, the modulation of the channels depth at their endpoints allows the surface contacting of the channel terminations with no need of further fabrication stages.In the present work we describe the sample masking, which includes the deposition of semi-spherical gold contacts on the sample surface, followed by MeV ion implantation.Because of the significant difference between the densities of pristine and amorphous or graphitized diamond, the formation of buried channels has a relevant mechanical effect on the diamond structure, causing localized surface swelling, which has been measured both with interferometric profilometry and atomic force microscopy. The electrical properties of the buried channels are then measured with a two point probe station: clear evidence is given that only the terminal points of the channels are electrically connected with the surface, while the rest of the channels extends below the surface. IV measurements are employed also to qualitatively investigate the electrical properties of the channels as a function of implantation fluence and annealing.

Fabrication and electrical characterization of three-dimensional graphitic microchannels in single crystal diamond

“…As shown in figure 2(b), the MeV ion implantation across such edges determines the formation of a highly damaged layer at a modulated depth, thus allowing the connection of the endpoint of the buried layer to the sample surface. The method described in this work represents a significant improvement over that reported in earlier works [42][43][44], allowing a reliable and reproducible lithographic process by means of variable-thickness masks with smoothly sloping edges, as reported in the profilometry scan reported in figure 2(c).…”

“…Cross-sectional TEM microscopy has been employed to directly image the emerging amorphized layers, which are formed upon the damage-induced conversion of the diamond lattice into a stable sp 2 phase, demonstrating the reliability of the variable-thickness masking technique, which has been optimized with respect to previous reports [42][43][44] to define amorphous structures in diamond with micrometric resolution in the three spatial dimensions.…”

“…Different methods have been explored to address this issue, such as laserinduced graphitization [39], high-voltage-induced thermal breakdown [40], multiple energy ion implantation [34] and laser ablation [41]. In a preliminary study [42], we proposed the use of 3D masks to modulate the penetration of MeV ions in diamond, thus allowing the direct ; the total number of vacancies per ion is 46, 47 and 52 for the three ion energies, respectively; the end-of-range damage peaks are clearly visible for all ion energies. and fast writing of 3D channels in the material with high spatial accuracy.…”

Modification of the structure of diamond with MeV ion implantation

“…Considerable effort has been devoted in recent years to the application of high energy (MeV) ion implantation in the fabrication and functionalization of diamond, in particular with the aim of developing a series of micro-devices, ranging from bio-sensors and detectors to micro-electromechanical systems (MEMS) and optical devices [1][2][3]. This can be achieved by exploiting the strongly non-uniform damage depth profile of MeV ions and creating specific regions where the diamond lattice structure is critically damaged.…”

Note: Laser ablation technique for electrically contacting a buried implant layer in single crystal diamond

“…[3][4][5][6][7] Depending upon implantation energy and ion species, this conducting layer will be a surface layer, or be buried under a thin, nearly pristine, single-crystal diamond skin; 2 however, making electrical contact through the insulating skin (∼50 nm at 150 keV) to the buried implant layer is not simple. A variety of techniques that achieve electrical contact by local conversion of the insulating diamond into a conducting medium are reported in the literature, such as: (1) Multiple ion implants, each at successively lower energies, 8 extend the conducting region from the buried layer to the surface; (2) Ion implantation into/through thin metal contacts or shaped masks 9,10 to laterally vary the depth of implantation damage from the buried layer to the surface; or (3) Pulsed laser conversion 11,12 of diamond channels to graphite.…”