Diamond-based UV and soft X-ray photodetectors E. Pace Dip. di ...

Figure captionsFigure 1 Absorption spectrum of CVDdiamond in the deep UV up in energies to thesoft X-ray region (data from ref. [2]).Figure 2 Reflectance of a single crystal naturaldiamond (data from ref. [16]).Figure 3 Micro-Raman spectrum of a nontexturedCVD diamond film obtainedilluminating a single grain at wavelength 514.5nm. The inset shows the linewidth of thediamond line (ref.[40]).Figure 4 Photocurrent versus the electric fieldfor a diamond-based photoconductor. The samebehaviour has been reported for two differentwavengths. At high electric field thephotocurrent saturates, since photogeneratedcharge is fully collected.Figure 5 X-Ray Diffraction patterns for 4different CVD diamond films, described in theTable 1. Table 1 explains also the meaning ofthe parameter p.Figure 6 Skecth of a typical diamondphotoconductor.Figure 7 SEM image of interdigitated Agcontacts on a textured diamond film. Thedistance between two metal strips is 12.5 µm.Figure 8 Schematic of the experimentalapparatus used for measurements in the vacuumUV (λ < 200 nm).Figure 9 Dark currents measured for diamondfilms having Ag ohmic contact (a,b), Au (c)and Ti-Au (d) rectifying contacts. Dark currentsin (a) and (b) are reported for planar andsandwich devices and they can be compared tothe same measurements performed in air.Figure 10 Quantum efficiency for a singlecrystal natural diamond (a) and a CVD-grownpolycrystalline diamond film (b) (data fromrefs. [3,32])Figure 11 Spectrum of a D 2 lamp in the 120-300 nm wavelength region (b,c,d) as detectedby three diamond photodetectors having planarelectric contacts. The same spectrum (a),recorded by an UV sensitive phosphor coatedphotomultiplier, has been reported forcomparison.Figure 12 Relative quantum efficiency of threediamond detectors with respect to thephotomultiplier. Quantum efficiency curve fora sandwich diamond device has been reportedfor comparison.Figure 13 Normalized responsivity of somediamond-based detectors: a microwave plasmaCVD-grown sample (i), a hot filament CVDgrownfilm (ii) and another microwave plasmaCVD-grown sample but nitrogen doped (iii).The curve (iv) is relative to sample (ii) after along UV exposure (data from ref. [32]).Figure 14 Comparison among photocurrentsproduced by several microwave plasma CVDgrownfilms. The preferential orientation hasbeen indicated to show the correlation betweenthe photocurrent and the film texture both inplanar and sandwich configurations.Figure 15 Plot showing the correlationbetween the photocurrent and the preferentialorientation of crystals in the diamond films(parameter p).Figure 16 Temporal behaviour ofphotocurrent.