- Email: [email protected]
Recent results on chemical-vapor-deposited diamond microstrip detectors
in
Nuclear Instruments and Methods
Physics Research A 380 ( 1996) 183-185
Recent results on chemical-vapor-deposited detectors
NUCLEAFI INSTFHJMEWTS & METHODS IN PHYSicS RESEARCH SectIonA
diamond microstrip
C. Bauer”, I. Baumann”, C. Colledanib, J. Conway”, P. Delpierre”, F. Djama”, W. Dulinskib, A. Falloud, K.K. Gan”, R.S. Gilmoref, E. Grigoriev”, G. Hallewell”, S. Hang’*, T. Hessingh, J. Hubec’, D. Hussonb. H. Kagan’, D. Kania’. R. Kasse. W. Kinnison’, K.T. Kntipfle”, M. Krammer’, T.J. Llewellyn’, P.F. Manfredik, L.S. Pan’, H. Pernegger’, M. Pernicka’, V. Rek, S. Roeh, A. Rudgeh, M. Schaefferh, S. Schnetzerc, S. Somalwa?, V. Spezialik, R. Stonec, R.J. Trapperf, R. Tesarek’, W. Trischukh, R. Turchettab. G.B. Thomson’, R. Wagner”, P. Weilhammerh, C. White”. H. Ziock”, M.M. Zoeller’ “MPI-Heidelberg. hLEPSI,
LRutgers
069029.
University. “CPPM,
‘Bri.stoi ‘Los
Akmos
‘Lawrence klJniversita
for
Akademie
Lir~ermore di Pavia.
‘Sundia
National
Furtick
Columbtts. 3ri.~tol, 858
Luborutory.
ITL,
NM 87545, USA
(CERNI.
Genera,
Livermorr.
di Elettronica. Livermore.
USA
UK
A- lOsO Vienna.
LLlboratoc.
Dipurtimento
USA
OH 432/O,
Los Alumus.
Physics
d. Wissmschaftm. Nutionul
NJ 088%.
13288. Frurzc~e
N~ti~~~~ ~tb~r~t~~~,
Luborntoty
‘Osterr.
Universi~.
Crrmun~
67037, Franc-e
Piscatawa~,
Mursriik.
‘The Ohio State Utrivrrsity.
“European
Heidelberg.
CRN. Strashourg.
Switxrhmd Austrict
CA 94250. USA
27100.
P&a.
It&
CA 94SS2. USA
Abstract Diamond is a nearly ideal material for detecting ionizing radiation. Its outstanding radiation hardness, fast charge collection, and low leakage current allow a diamond detector to be used in high-radiation high-tem~rature and aggressive chemical environments. We report here the results of recent beam tests of chemical-vapor-deposited diamond microstrip detectors in a 100 GeV pion beam at CERN, Geneva. Switzerland. Using detectors with a 50 pm strip pitch and a 50% coverage, we achieved an average signal size of 4350 electrons with a signal-to-noise ratio of 30: I and a spatial resolution of 14.3 I*m.
1. Introduction During the past year we have constructed and tested a series of Chemical-Vapor-Deposited (CVD) diamond microstrip tracking detectors. Diamond is an interesting material for position-sensitive tracking devices because of its fast response, lower noise associated with reduced capacitance due to lower dielectric constant and extremely low leakage current, and extreme radiation hardness. Recent results indicate that the present detector grade diamond shows no degradation for photon doses of IO *Corresponding author. 01~8-~~/96/$15.~ Pii
Mrad [I), 300 MeV/c pion fluence levels of 10’J/cm’ [2]. and 500 MeV proton fluence levels of 10’Jlcm’ [3]. Furthermore, detectors can be made into simple metalsemiconductor-metal device with no need for junctions. As a result, tracking detectors with diamond as the active detector material are already ideal candidates for environments where radiation hardness is a primary concern along with a need for fast response. Our work on diamond microstrip devices began with 100 pm-pitch detectors. The complete details and results from these tests may be found in work reported previously [4-61. In this note we report results as a part of work-inprogress from data taken in 1995 using the first 50 pm-
Copyright 01996 Published by Elsevier Science B.V. All rights reserved
SOlhg-g00’(96t00376-1
ii(a).
ELEMENTARY
MODULES
C. Bauer et al. I Nucl. Instr. and Meth. in Phys. Res. A 380 (1996)
184
pitch detectors. This work was performed Diamond Detector Collaboration at CERN.
2. Experimental
by the RD42
procedure
2. I. Detector fabrication The as-received diamond films were first degreased with various organic solvents followed by a clean in hot chromic acid which was prepared as a saturated solution of chromium trioxide in sulfuric acid. The hot chromic acid clean has been shown to eliminate any graphite or nondiamond material, such as amorphous carbon from the surfaces of diamond [7-lo]. After this step, the samples were rinsed in de-ionized water followed by rinses in 0.1 M NH,OH, 0.1 M HCI, and concentrated HF. Then, the samples were rinsed in de-ionized water and dried. At this point, the samples were considered ready for processing into detectors. The devices were fabricated by first metallizing the substrate side of the diamond with 500 A of titanium and 3000 A of gold using a high-vacuum sputter deposition system, and then patterning the metal using a combination of photolithography and wet-etch processes. The side opposite the strip pattern consisted of a continuous Ti/Au electrode applied using the same metal deposition procedure after the strips were defined. After the fabrication, the devices were annealed at 450°C for about 10 min. 2.2. Measurement
183-185
procedure
In 1995 the RD42 group tested 50 pm-pitch CVD diamond trackers in a 100 GeV pion beam line (X5) at CERN. The diamond test devices were positioned in a telescope consisting of eight planes of silicon strip reference detectors. The reference detectors were single-sided, AC-coupled FOXFET biased, 19.2 mm X 19.2 mm devices with an implant/readout pitch of 25/50 pm [I I]. The silicon detectors were arranged in 4 X-Y pairs so that an incoming pion trajectory could be determined unambiguously. The silicon detectors were operated at 70 V; diamond detectors were operated at 300 V. The silicon detectors were equipped with low-noise VIKING readout electronics [ 121; the diamond test trackers were equipped with newer VA-2 electronics. The electronics for both the silicon and the diamond was operated with a 2 (*s shaping time resulting in typical noise levels of 150 electrons for the silicon detectors and 100 electrons noise for the diamond detectors. The precision of the individual silicon detectors was approximately 4-5 km which resulted in an extrapolation error at the diamond tracker of l-2 brn. The preliminary results shown below were extracted from 355 000 raw data triggers incident normally to the telescope.
Fig.
1.
A
side view of a 50 km-pitch diamond microstrip detector.
3. Results In Fig. 2(a) the pulse height distribution is shown for all good tracks found in the silicon which project into the accepted fiducial region of the diamond detector. This distribution has a mean signal charge of 124 ADC counts and a most probable signal charge of 85 ADC counts. Using the average gain of the system (35 e/ADC count) we find an average signal size of 4350 electrons and a most probable signal size of 3000 electrons. With the measured noise of 100 electrons for the diamond detector, the most probable signal-to-noise ratio of 30:1 is realized. The signal size corresponds to a collection distance of 121 pm where the collection distance is the average distance an electron-hole pair moves apart under the influence of the electric field. In Fig. 2(b) we show the preliminary spatial resolution obtained for the same detector. This distribution was produced by comparing the predicted location from the silicon telescope with the measured location using the two strips with the largest pulse height. The distribution has a width of 14.3 pm. This resolution is what was expected for digital resolution. This result should improve somewhat as the measured position algorithm improves.
4. Conclusions The results shown here for the pulse height distribution or charge collected represent a factor of four improvement over those of a year ago. The most probable signal-to-noise of 3O:l attained with the 2 p.s shaping time means that such diamond microstrip detectors could be used in experiments which can tolerate the long shaping time. During the next year we expect to gain another factor of two in signal size which will allow us to operate diamond microstrip devices at much faster shaping times.
Acknowledgments A portion of this work was performed under the auspices of the U.S. Department of Energy by Los Alamos National Laboratory under Contract No. W-7405-Eng-48.
C. Bauer et al. / Nucf. instr. and Me&
in Phys. Res. A 380 (f996)
183-185
185
Fig. 2. (a) The pulse height dis~bution from a diamond microstrip detector derived fmm the two strips closest to the track projected from the silicon telescope. (b) The position resolution derived by comparing the measured hit location in the diamond using a two-strip algorithm with the predicted location from the silicon telescope.
References [I] H. Pernegger et al., Nucl. Instr. and Meth. A 367 (1995) 207. [2] C. Bauer et al., Pion I~adiation Studies of CVD Diamond Detectors. 131 C. Bauer et al., Proton Irmdiation Studies of CVD Diamond Detectors, in preparation. I41 F. Borcheit et al., Nucl. Instr. and Meth. A 354 (1995) 318. [S] C. White et al., Nucl. Instr. and Meth. A 351 (1994) 217. [6] W. Dulinski et al.. Nucl. Instr. and Meth. A 367 (1995)202. 171 L.S. Pan, S. Han, D.R. Kannia and K. Okano, Diamond Films and Tech. 2 (1992) 99.
PI S.A Grot, S. Lee, G. Sh. Gildenblat. C,W. Hatfield, CR. Wronski, A.R. Badzian, T. Badzian and R. Messier, IEEE Elec. Dev. Lett. 11 (2) (1990) 100. I91 S.A. Grot, S. Lee. G. Sh. Gildenblat, C.W. Hatfield, CR. Wronski, A.R. Badzian. T. Badzian and R. Messier. J. Mater. Res, 5 ( 1990) 2497. IH)l Y. Mori, H. Kawarada and A. Hiraki, Appl. Phys. Lett. 58 11991) 940. 1111 The silicon detectors were produced by CSEM, Maladiere 71, Case Postale 41, Neuchatel, Switzerland CH-2007. r121 P. Aspell et al., Nucl. Instr. and Meth. A 315 (1992) 425.
II(a). ~LE~~~ARY
MODULES
Nuclear Instruments and Methods
Physics Research A 380 ( 1996) 183-185
Recent results on chemical-vapor-deposited detectors
NUCLEAFI INSTFHJMEWTS & METHODS IN PHYSicS RESEARCH SectIonA
diamond microstrip
C. Bauer”, I. Baumann”, C. Colledanib, J. Conway”, P. Delpierre”, F. Djama”, W. Dulinskib, A. Falloud, K.K. Gan”, R.S. Gilmoref, E. Grigoriev”, G. Hallewell”, S. Hang’*, T. Hessingh, J. Hubec’, D. Hussonb. H. Kagan’, D. Kania’. R. Kasse. W. Kinnison’, K.T. Kntipfle”, M. Krammer’, T.J. Llewellyn’, P.F. Manfredik, L.S. Pan’, H. Pernegger’, M. Pernicka’, V. Rek, S. Roeh, A. Rudgeh, M. Schaefferh, S. Schnetzerc, S. Somalwa?, V. Spezialik, R. Stonec, R.J. Trapperf, R. Tesarek’, W. Trischukh, R. Turchettab. G.B. Thomson’, R. Wagner”, P. Weilhammerh, C. White”. H. Ziock”, M.M. Zoeller’ “MPI-Heidelberg. hLEPSI,
LRutgers
069029.
University. “CPPM,
‘Bri.stoi ‘Los
Akmos
‘Lawrence klJniversita
for
Akademie
Lir~ermore di Pavia.
‘Sundia
National
Furtick
Columbtts. 3ri.~tol, 858
Luborutory.
ITL,
NM 87545, USA
(CERNI.
Genera,
Livermorr.
di Elettronica. Livermore.
USA
UK
A- lOsO Vienna.
LLlboratoc.
Dipurtimento
USA
OH 432/O,
Los Alumus.
Physics
d. Wissmschaftm. Nutionul
NJ 088%.
13288. Frurzc~e
N~ti~~~~ ~tb~r~t~~~,
Luborntoty
‘Osterr.
Universi~.
Crrmun~
67037, Franc-e
Piscatawa~,
Mursriik.
‘The Ohio State Utrivrrsity.
“European
Heidelberg.
CRN. Strashourg.
Switxrhmd Austrict
CA 94250. USA
27100.
P&a.
It&
CA 94SS2. USA
Abstract Diamond is a nearly ideal material for detecting ionizing radiation. Its outstanding radiation hardness, fast charge collection, and low leakage current allow a diamond detector to be used in high-radiation high-tem~rature and aggressive chemical environments. We report here the results of recent beam tests of chemical-vapor-deposited diamond microstrip detectors in a 100 GeV pion beam at CERN, Geneva. Switzerland. Using detectors with a 50 pm strip pitch and a 50% coverage, we achieved an average signal size of 4350 electrons with a signal-to-noise ratio of 30: I and a spatial resolution of 14.3 I*m.
1. Introduction During the past year we have constructed and tested a series of Chemical-Vapor-Deposited (CVD) diamond microstrip tracking detectors. Diamond is an interesting material for position-sensitive tracking devices because of its fast response, lower noise associated with reduced capacitance due to lower dielectric constant and extremely low leakage current, and extreme radiation hardness. Recent results indicate that the present detector grade diamond shows no degradation for photon doses of IO *Corresponding author. 01~8-~~/96/$15.~ Pii
Mrad [I), 300 MeV/c pion fluence levels of 10’J/cm’ [2]. and 500 MeV proton fluence levels of 10’Jlcm’ [3]. Furthermore, detectors can be made into simple metalsemiconductor-metal device with no need for junctions. As a result, tracking detectors with diamond as the active detector material are already ideal candidates for environments where radiation hardness is a primary concern along with a need for fast response. Our work on diamond microstrip devices began with 100 pm-pitch detectors. The complete details and results from these tests may be found in work reported previously [4-61. In this note we report results as a part of work-inprogress from data taken in 1995 using the first 50 pm-
Copyright 01996 Published by Elsevier Science B.V. All rights reserved
SOlhg-g00’(96t00376-1
ii(a).
ELEMENTARY
MODULES
C. Bauer et al. I Nucl. Instr. and Meth. in Phys. Res. A 380 (1996)
184
pitch detectors. This work was performed Diamond Detector Collaboration at CERN.
2. Experimental
by the RD42
procedure
2. I. Detector fabrication The as-received diamond films were first degreased with various organic solvents followed by a clean in hot chromic acid which was prepared as a saturated solution of chromium trioxide in sulfuric acid. The hot chromic acid clean has been shown to eliminate any graphite or nondiamond material, such as amorphous carbon from the surfaces of diamond [7-lo]. After this step, the samples were rinsed in de-ionized water followed by rinses in 0.1 M NH,OH, 0.1 M HCI, and concentrated HF. Then, the samples were rinsed in de-ionized water and dried. At this point, the samples were considered ready for processing into detectors. The devices were fabricated by first metallizing the substrate side of the diamond with 500 A of titanium and 3000 A of gold using a high-vacuum sputter deposition system, and then patterning the metal using a combination of photolithography and wet-etch processes. The side opposite the strip pattern consisted of a continuous Ti/Au electrode applied using the same metal deposition procedure after the strips were defined. After the fabrication, the devices were annealed at 450°C for about 10 min. 2.2. Measurement
183-185
procedure
In 1995 the RD42 group tested 50 pm-pitch CVD diamond trackers in a 100 GeV pion beam line (X5) at CERN. The diamond test devices were positioned in a telescope consisting of eight planes of silicon strip reference detectors. The reference detectors were single-sided, AC-coupled FOXFET biased, 19.2 mm X 19.2 mm devices with an implant/readout pitch of 25/50 pm [I I]. The silicon detectors were arranged in 4 X-Y pairs so that an incoming pion trajectory could be determined unambiguously. The silicon detectors were operated at 70 V; diamond detectors were operated at 300 V. The silicon detectors were equipped with low-noise VIKING readout electronics [ 121; the diamond test trackers were equipped with newer VA-2 electronics. The electronics for both the silicon and the diamond was operated with a 2 (*s shaping time resulting in typical noise levels of 150 electrons for the silicon detectors and 100 electrons noise for the diamond detectors. The precision of the individual silicon detectors was approximately 4-5 km which resulted in an extrapolation error at the diamond tracker of l-2 brn. The preliminary results shown below were extracted from 355 000 raw data triggers incident normally to the telescope.
Fig.
1.
A
side view of a 50 km-pitch diamond microstrip detector.
3. Results In Fig. 2(a) the pulse height distribution is shown for all good tracks found in the silicon which project into the accepted fiducial region of the diamond detector. This distribution has a mean signal charge of 124 ADC counts and a most probable signal charge of 85 ADC counts. Using the average gain of the system (35 e/ADC count) we find an average signal size of 4350 electrons and a most probable signal size of 3000 electrons. With the measured noise of 100 electrons for the diamond detector, the most probable signal-to-noise ratio of 30:1 is realized. The signal size corresponds to a collection distance of 121 pm where the collection distance is the average distance an electron-hole pair moves apart under the influence of the electric field. In Fig. 2(b) we show the preliminary spatial resolution obtained for the same detector. This distribution was produced by comparing the predicted location from the silicon telescope with the measured location using the two strips with the largest pulse height. The distribution has a width of 14.3 pm. This resolution is what was expected for digital resolution. This result should improve somewhat as the measured position algorithm improves.
4. Conclusions The results shown here for the pulse height distribution or charge collected represent a factor of four improvement over those of a year ago. The most probable signal-to-noise of 3O:l attained with the 2 p.s shaping time means that such diamond microstrip detectors could be used in experiments which can tolerate the long shaping time. During the next year we expect to gain another factor of two in signal size which will allow us to operate diamond microstrip devices at much faster shaping times.
Acknowledgments A portion of this work was performed under the auspices of the U.S. Department of Energy by Los Alamos National Laboratory under Contract No. W-7405-Eng-48.
C. Bauer et al. / Nucf. instr. and Me&
in Phys. Res. A 380 (f996)
183-185
185
Fig. 2. (a) The pulse height dis~bution from a diamond microstrip detector derived fmm the two strips closest to the track projected from the silicon telescope. (b) The position resolution derived by comparing the measured hit location in the diamond using a two-strip algorithm with the predicted location from the silicon telescope.
References [I] H. Pernegger et al., Nucl. Instr. and Meth. A 367 (1995) 207. [2] C. Bauer et al., Pion I~adiation Studies of CVD Diamond Detectors. 131 C. Bauer et al., Proton Irmdiation Studies of CVD Diamond Detectors, in preparation. I41 F. Borcheit et al., Nucl. Instr. and Meth. A 354 (1995) 318. [S] C. White et al., Nucl. Instr. and Meth. A 351 (1994) 217. [6] W. Dulinski et al.. Nucl. Instr. and Meth. A 367 (1995)202. 171 L.S. Pan, S. Han, D.R. Kannia and K. Okano, Diamond Films and Tech. 2 (1992) 99.
PI S.A Grot, S. Lee, G. Sh. Gildenblat. C,W. Hatfield, CR. Wronski, A.R. Badzian, T. Badzian and R. Messier, IEEE Elec. Dev. Lett. 11 (2) (1990) 100. I91 S.A. Grot, S. Lee. G. Sh. Gildenblat, C.W. Hatfield, CR. Wronski, A.R. Badzian. T. Badzian and R. Messier. J. Mater. Res, 5 ( 1990) 2497. IH)l Y. Mori, H. Kawarada and A. Hiraki, Appl. Phys. Lett. 58 11991) 940. 1111 The silicon detectors were produced by CSEM, Maladiere 71, Case Postale 41, Neuchatel, Switzerland CH-2007. r121 P. Aspell et al., Nucl. Instr. and Meth. A 315 (1992) 425.
II(a). ~LE~~~ARY
MODULES