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Applications of diamond films Lecture 5. CVD diamond devices and components microwave transistor on diamond wafer UV and X-ray detectors IR windows for.

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Presentation on theme: "Applications of diamond films Lecture 5. CVD diamond devices and components microwave transistor on diamond wafer UV and X-ray detectors IR windows for."— Presentation transcript:

1 Applications of diamond films Lecture 5

2 CVD diamond devices and components microwave transistor on diamond wafer UV and X-ray detectors IR windows for gyrotron and CO 2 lasers X-ray lenses and screens thin membranes Cutting tools

3 CVD diamond thermal spreaders for microwave electronic devices (transistors). Examples of size: 4.6 х 0.9 х 0.5 мм 8.6 х 1.4 х 0.5 мм

4 Thin diamond films on AlN ceramics AlN dielectric heat spreader, 18 mm diameter. Diamond coating increases thermal conductivity from 1.7 to 10.0 W/cmK. AlN before diamond ► deposition ◄ Coated with black diamond V.G. Ralchenko, Russian Microelectronics, 2006, Vol. 35, No. 4, p growth rate 7.9 μm/h; film thickness up to 150 μm Thermal conductivity measurements by laser flash technique

5 CVD diamond detectors D. Meier, RD42 Collaboration Rep Charge collection distance d = µτE RD42 Collaboration (CERN) data for De Beers CVD diamond samples (poly): d = 200 µm (year 2000) d max ≈ 350 µm present Stable up to dose ~10 15 cm -2 under protons, neutrons, pions. GPI samples

6 CVD diamond UV detectors solar-blind photoresistors Interdigitizing electrodes on polished diamond. Cr(20 nm)/Au(500nm) strips 50 µm wide, the gap between electrodes is 50 µm. Spectral discrimination UV/Vis of Dark current of the order of 1 pA. V.G. Ralchenko et al. Quantum Electronics (Moscow, 36 (2006) 487. Photoresponse of nucleation (1) and growth sides

7 GPI-RAS Diamond Spectral Photonductivity: JDoS Low surface recombination and small Urbach tail. The recovery of photoconductivity is more than 6 orders of magnitude and saturates around 5 V/µm. Band gap E g = 5.45 eV. Light absorption and e-h pairs generation for photons with λ <225 nm, no absorption in the visible and IR. ► solar-blind radiation-hard photodetectors (no filters are needed) SC CVD diamond UV detectors

8 2D-UV detector: mapping the laser beam 16-pixel matrix sensor on 1 cm 2 polycrystalline diamond: G. Mazzeo et al. DRM. 16 (2007) 1053 Rows and columns are electrodes on two sides of the diamond sample. Sensor electronics Output signal : 1 mm 2 beam illuminates the pixels along the row direction. incident measured Test monochromatic beam profile

9 M. Girolami, P. Allegrini, G. Conte, S. Salvatori, D. M. Trucchi, A. Bolshakov, V. Ralchenko “Diamond detectors for UV and X-ray source imaging”, IEEE-EDL 33 (2012) Past UV, X-ray Source Imaging 36-pixel array (0.75 × 0.75 mm 2 ) Poly 1 cm 2 RAS 270 um Contacts – Ag nm Cu-K a, 8.05 keV ArF 193 nm, 3 mW UV, X-ray Source Imaging by 2D detectors X-ray tube beam profile when scanned across the detector ArF excimer laser beam profile

10 On-line diamond X-ray detectors Diamond membrane: 11 µm thickness, window of 7 mm diameter. Source: X-ray tube with tungsten anode. Electrodes Au/Ti, Ø3 mm. Dark current ~100pA. Photocurrent/dark-current ratio: 8x10 3 at U a =50 kV, j=15 mA. X-ray transmission (50 keV) > 98%. V. Dvoryankin et al. Lebedev Physical Institute Reports, No. 9 (2006) 44.

11 p-type conductivity on H-terminated diamond surface: 2D hole layer H diamond H-terminated layer Microwave plasma less than 6 nm Hole density is evaluated from C-V characteristics G. Conte et al, NGC 2011, Moscow 1994: H-terminated diamond based FET H. Kawarada, et al., Appl. Phys. Lett. 65 (111) Surface with C-H bonds Surface band bending where valence-band electrons transfer into an adsorbate layer: “transfer doping model”. Shallow hydrogen induced acceptors. ♦ carriers density value cm -2 ♦ hole mobility cm 2 /Vs ♦ activation energy meV

12 Device Layout 25 μm ≤ W G ≤ 200 μm 0.2 μm ≤ L G ≤ 1 μm Small H-terminated area for leakage current reduction and electric field confinement. 2D Hole Channel Drain (Au) Gate (Al) Source (Au) CVD Diamond WGWG Device Technology Issues MESFET technology issues Batterfy-shaped design

13 -20 dB/dec. V GS =-0.2 V, V DS =-10 V Gain = 15 1 GHz E applied = 0.5 MV/cm W G =25 μm f MAX = 23.7 GHz f T = 6.9 GHz Polycrystalline Diamond RAS PolyD4 f MAX /f T =3.5 L G =0.2 μm Past Surface Channel MESFETs G. Conte, E. Giovine, A. Bolshakov, V. Ralchenko, V. Konov “Surface Channel MESFETs on Hydrogenated Diamond”, Nanotechnology 23 (2012) Single Crystal Diamond RAS P7MS W g =50 μm f MAX =26.3 GHz f T = 13.2 GHz Gain = 22 1 GHz f MAX /f T =1.8 MESFET frequency characteristics

14 1- buried graphite; 2 - contacts Fast CVD diamond bolometer Very thin buried graphitized layer as resistor. Fast dissipation of absorbed energy – quick response. Fabrication procedure: (i) C + ion implantation in polished CVD diamond: energy 350 keV, dose 8  cm -2. (ii) Contacts – graphitic pillars by C + implantation at variable energy of 20 to 350 keV. (iii) Annealing in vacuum at 1500ºC for 1 hour. ► Buried graphite strip: 2 mm total length, 70 μm wide, thickness 220 nm, depth 265 nm. Segments of 70 and 300 μm long. K is R 0 = Ohm. Linear temperature dependence R(T)=(-1.47  K -1 )R 0 T.I. Galkina, Physics of Solid State (St. Petersburg), 49 (2007) 621.

15 Test of diamond bolometer Pulsed irradiation with a nitrogen laser (λ=337 nm, τ~ 8 ns). Beam spot size 90 μm. Measured signal (circles) and modeling (solid line). Response signal ≈20 ns (FWHM), very fast for bolometer-type sensors Layered structure for simulation of the bolometer response kinetics.

16 Raman diamond lasers use Stimulated Raman Scattering (SRS) For polycrystalline CVD diamond: Kaminskii, V. Ralchenko, et al. Phys. Stat. Sol. (b), (2005). For single crystal CVD diamond: A.A.Kaminskii, R.J. Hemley, et al. Laser Phys. Lett. (2007). Stokes and anti-Stokes lines. SRS intensity comparable to pump pulsed pump Single pass geometry ● SRS is observed only at high enough intensities. ● Advantages of diamond: - large Raman shift 1332 cm-1 - high gain g>11 cm/GW. spontaneous RS stimulated RS excitation at λ=1.06 µm; three anti-Stokes lines

17 Wavelength conversion range achieved experimentally polycrystalline CVD diamond Excitation wavelengths: 0.53 μm, 1.06 μm, 1.32 μm Pulse duration: 15 ns, 10 ps and 80 ps. Yellow emission at 573 nm; 5 kHz (ns), 1.2 W output power; conversion efficiency of 63.5%. 2.2 W with ps pulses (2010) Single crystal are more efficient. Raman laser on SC CVD diamond: R. Mildren et al. Opt. Lett. (2009) Latest result: A continuous-wave (cw) operation of a diamond Raman laser at 1240 nm with power 10.1 W. A. McKay et al. Laser Phys. Lett., 10 (2013)

18 Commercial SRS-active crystalline materials with laser frequency shift (ω SRS ) more than 850 cm -1 A.A. Kaminskii, Laser Physics Letters, 3 (2006) 171.

19 Institute of Photonics, University of Strathclyde, UK Industrial Diamond Rev. No. 4, Diamond Raman laser

20 C. Wild, SMSA 2008, Nizhny Novgorod

21 Diamond window for IR cw lasers ANSYS program, finite element analysis. ● all absorbed heat dissipates via cooled edges. ●Laser parameters: beam diameter 10 mm; incident power 5.0 kW; absorption coeff.  =0,1 см-1 (at 10.6 μm). Result - heating ΔT<9°C. Modeling: radial temperature profile CVD diamond, 25 mm diameter, 1.2 mm thickness Experiment: Exposed to a fiber Nd:YAG cw laser for 1 min; power 10.0 kW, beam diameter 5 mm, Result - window survived V.E. Rogalin et al. Russian Microelectronics, 41 (2012) 26.

22 Gyrotrons – generators of powerful mm waves (~ GHz)  very low absorption (low loss tangent)  high mechanical strength (Young’s modulus, E)  low dielectric permittivity, .  low thermal expansion coefficient,   high thermal conductivity, k, Properties of some materials important for mm-waves windows (T=293 K and f=145 GHz) Material  tan  (10 -4 ) k W/cmK  K -1 E GPa Fused quartz BN BeO Sapphire Au-doped Si Diamond * 0.03** *Diagascrown/GPI sample [B. Garin et al. Techn. Phys. Lett. 25 (1999) 288] **DeBeers sample [V. Parshin et al. Proc. 10th Int. ITG-Conf. on Displays and Vacuum Electronics, 2004 **DeBeers sample [V. Parshin et al. Proc. 10th Int. ITG-Conf. on Displays and Vacuum Electronics, 2004] Requirements to gyrotron window material:

23 Vacuum-tight CVD diamond windows brazed to copper cuffs TESTS Thermal cycling: ●  C and (–60)-(+150)  C ● 8 hours heating at 650  C. No degradation in vacuum tightness. Window diameter 60 mm and 15 mm Loss tangent ~ V. Parshin, 4th Int. Symp. Diamond Films and Relat. Mater., Kharkov, Ukraine, 1999, p. 343.

24 CVD diamond to manage synchrotron radiation Synchrotrons generate extremely bright radiation by electrons orbiting in magnetic field with speed close to velocity of light. Photons in a broad IR to X-ray range; power density of hundreds W/mm 2. Diamond instead of Si for: ● beam attenuators; ● fluorescent screen for beam monitoring; ● X-ray and UV detectors, ● monochromators (first tested at European Synchrotron, Grenoble, in 1992), (only single crystals appropriate) Synchrotron Soleil, Paris Water cooled IR window from Diamond Materials, Germany

25 Transmission of 0–20 keV radiation through 20 μm thick beryllium, diamond and silicon. High transparency of diamond for X-rays can be utilized for making X-ray lenses C. Ribbing et al. Diamond Relat. Mater. 12 (2003) 1793.

26 Principle of X-ray focusing by a refractive lens For X-rays refractive index n=1-δ, (δ<<1) ► a hole acts as the lens

27 X-ray diamond lenses of 15 x 40 mm 2 size with relief depth of 100 and 200 μm. Four parabolic lenses are formed on each 110 μm thick diamond plate. Diamond films of ca. 110  m thickness Refractive CVD diamond X-ray lens produced by molding technique Geometry of X-ray focusing test. A. Snigirev, Proc. SPIE, Vol (2002) p. 1. Lens test at synchrotron (ESRF, Grenoble): Beam focusing at 2 μm diameter; focal distance 50 cm; lens gain: X-ray transmission 38 keV; X-ray power density 50 W/mm 2 – long term (16 hours) stability (experiment); up to 500 W/mm 2 – acceptable (simulation).

28 C.-S. Zha et al. High Pressure Research, 29 (2009) 317 CVD diamond anvils for high-pressure/high-temperature experiments CVD-based diamond anvils have strength that is at least comparable to and potentially higher than anvils made of natural diamond. Reparation of damaged anvil combined CVD-natural diamond anvil. CVD-covered anvil immediately after the growth. The same anvil after removing of the polycrystalline material, reshaping, and polishing to anvil with 30μm in diameter of the center flat culet. Test: successful HPHT measurements on hydrogen at megabar pressures.

29 Opal (and inverse opal) as photonic crystal opal and inverse opal structures A.A. Zakhidov, Science, 282 (1998) 897. Silica opals are made by self- assembly of SiO 2 spheres into face- centered cubic (fcc) crystals. The narrowest channel (pore) diameter ≤ 39 nm for balls of 250 mm diameter. Pores in opal lattice can be filled with other materials to make a composite or inverse structure (replica).

30 A.A. Zakhidov, Science, 282 (1998) 897. Diamond inverse opal produced by replica technique Seeding with ND partciles, diamond deposition in microwave plasma

31 Inverted opal made of amorphous Si Produced at A. Ioffe Phys.Technical Inst. RAS, St. Petersburg Period 310 nm, pore diameter ~100 nm. Plate thickness 400 µm. Thermal decomposition of SiH 4 in pores of SiO 2 opal, followed by SiO 2 matrix etching. Seeding with ND Inverted Si opal – porous structure

32 Direct opal diamond L = 310 nm, 25 layers of spheres Diamond opal. Cross section 10 µm below the growth surface. Raman spectra excited in UV (244 nm), top, and in the visible (488 nm), bottom, regions Next step: diamond deposition in Si opal template followed by the Si etching. A lot of a-C and graphite in the deposit. Graphite etching by oxidation in air at Т = 500ºС. Clear diamond peak at 1332 cm -1 in UV. Still graphite-like is present. Sovyk D. N. et al. Physics of the solid state. 55 (2013) 1120.

33 Diamond shells (20 nm thick) with nanographite partciles inside.(111) face. Diamond opal as photonic crystal Reflection spectra from inversed Si opal (period 310 nm) and direct diamond opal (period 260 nm) at angle 11° to (111) plane. Bragg reflection peaks are clearly observed. D-opal Si inversed opal

34 Conclusions ● Polycrystalline diamond films and single crystals of high purity and large size can be produced by CVD technique. ● The properties of CVD diamond approach (in some cases exceed) those known for the best natural single crystal diamonds. ● Potential application of the CVD diamond include, in particular: -- detectors of ionizing radiation; -- X-ray, optics, IR and microwave optics for CO 2 lasers, gyrotrons, etc; -- radiation-hard, high-temperature, high-power electronic devices; -- Raman lasers -- GHz-range devices based on surface acoustics waves; -- new applications…

35 GPI Diamond Materials Lab


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