Chapter 2. Diamond Detectors with Graphite Contacts Chapter 2 Diamond Detectors with Graphite Contacts P. Oliva, S. Salvatori, G. Conte, A. P. Bolshakov, V. G. Ralchenko 1 2.1. Introduction Diamond and graphite are materials with opposite properties although the chemical composition is the same: pure carbon. The main difference being the bond among carbon atoms. While natural diamond is widespread in jewelry, graphite has demonstrated to be suitable in many fields of the electrical technology from brushes in rotant bodies of dynamos to sliding contacts in rotary potentiometers, as electrode in metallurgical arc- furnaces and solid-state batteries. Such applications are due to the excellent mechanical and electrical features deriving on its particular morphology and structure. Indeed, carbon shows very different morphology and physical properties: the crystalline instable form, the diamond, uses sp 3 orbitals to develop the very tight lattice and the highest mechanical hardness (10 on Mohs scale, 70000 on the Knoop ones), the most resilient material, suitable for cutting tools fabrication whereas, graphite, the termodinamically stable form, shows sp 2 ibridization. Whilefor diamond a high energy is necessary to displace a single atom from the tight lattice (1.76×10 23 at/cm 3 ), graphite has ordered carbon planes able to slide one respect the other and leading to excellent lubricant properties. Other important properties arising from the carbon bond organization are the density of diamond (3.54 g/cm 3 ) while graphite is 2.3 g/cm 3 ; diamond has a wide band gap energy (5.47 eV at 300 K) [1] with transparency in a wide radiation range, insulating electrical properties (σ < 10 -15 S/cm) and a low dielectric constant (5.7), graphite appears black with evident anisotropic metal-like conductivity (~1.3×10 3 S/cm). Moreover, the very high thermal conductivity of single crystal diamond (22 W/cm K), concurrently with the mechanical and electronic features, ensure power dissipation, temperature stability and radiation hardness while graphite with its absorption properties gives the possibility to work in daylight. All such characteristics are fundamental for the fabrication of detectors operating at inclement environments, in daylight, in which other semiconductor devices cannot properly work as under intense excimer lasers sources [2], synchrotron radiation beam lines and flux of nuclear particles produced in high-energy physics experiment. On the other hand, one of the most important issues of diamond detectors fabrication is the P. Oliva University Niccolò Cusano, Roma, Italy