TABLE OF CONTENTS Whilst SiC is hard and durable, diamond is even more so and exhibits a number of unique properties that give rise to several sensor applications. Some of these properties are listed below:
Extreme mechanical hardness (~90GPa).
High wear resistance.
Highest bulk modulus (1.2 10 12Nm 2).
Lowest compressibility (8.3 10 13m 2 N 1).
Highest room temperature thermal conductivity (2 10 3Wm 1 K 1).
Thermal expansion coefficient at room temperature very low (1 10 6K).
Broad optical transparency from the deep UV to the far IR.
Highest sound propagation velocity (17.5km s -1 ).
Very good electrical insulator (room temperature resistivity is ~10 13W ?cm).
Diamond can be doped, becoming a semiconductor with a wide band gap of 5.4eV.
High tolerance to ionising radiations.
Very resistant to chemical corrosion.
Some of the above open up a number of radiation sensing opportunities and diamond s large band gap of 5.4eV (225nm, i.e. in the far vacuum UV), is such that photodetectors fabricated from this material should be blind to visible light whilst being sensitive in the deep UV region. However, real diamond exhibits significant extrinsic photoconductivity leading to a strong signal when exposed to visible light and early CVD diamond was even worse as it was typically so defective that most charge carriers were lost before detection. Early attempts to fabricate diamond UV photodetectors were disappointing but recently the first truly visible-blind...
