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A 3D diamond detector for particle tracking
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DOI:10.1016/j.nima.2015.09.079
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“A 3D Diamond Detector for Particle Tracking”
M. Artuso et al. (RD42 Collaboration)
Nuclear Instruments and Methods in Physics Research A
DOI: 10.1016/j.nima.2015.09.079 (2016)
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Author’s Accepted Manuscript
A 3D Diamond Detector for Particle Tracking
M. Artuso, F. Bachmair, L. Bäni, M. Bartosik, J.
Beacham, V. Bellini, V. Belyaev, B. Bentele, E.
Berdermann, P. Bergonzo, A. Bes, J-M. Brom, M.
Bruzzi, M. Cerv, C. Chau, G. Chiodini, D. Chren,
V. Cindro, G. Claus, J. Collot, S. Costa, J.
Cumalat, A. Dabrowski, R. D'Alessandro, W. de
Boer, B. Dehning, D. Dobos, M. Dünser, V.
Eremin, R. Eusebi, G. Forcolin, J. Forneris, H.
Frais-Kölbl, K.K. Gan, M. Gastal, M. Goffe, J.
Goldstein, A. Golubev, L. Gonella, A. Gorišek, L.
Graber, E. Grigoriev, J. Grosse-Knetter, B. Gui, M.
Guthoff, I. Haughton, D. Hidas, D. Hits, M.
Hoeferkamp, T. Hofmann, J. Hosslet, J-Y.
Hostachy, F. Hügging, H. Jansen, J. Janssen, H.
Kagan, K. Kanxheri, G. Kasieczka, R. Kass, F.
Kassel, M. Kis, G. Kramberger, S. Kuleshov, A.
Lacoste, S. Lagomarsino, A. Lo Giudice, C.
Maazouzi, I. Mandic, C. Mathieu, N. McFadden,
G. McGoldrick, M. Menichelli, M. Mikuž, A.
Morozzi, J. Moss, R. Mountain, S. Murphy, A. Oh,
P. Olivero, G. Parrini, D. Passeri, M. Pauluzzi, H.
Pernegger, R. Perrino, F. Picollo, M. Pomorski, R.
Potenza, A. Quadt, A. Re, G. Riley, S. Roe, M.
Sapinski, M. Scaringella, S. Schnetzer, T.
Schreiner, S. Sciortino, A. Scorzoni, S. Seidel, L.
Servoli, A. Sfyrla, G. Shimchuk, D.S. Smith, B.
Sopko, V. Sopko, S. Spagnolo, S. Spanier, K.
Stenson, R. Stone, C. Sutera, A. Taylor, M.
Traeger, D. Tromson, W. Trischuk, C. Tuve, L.
Uplegger, J. Velthuis, N. Venturi, E. Vittone, S.
Wagner, R. Wallny, J.C. Wang, P. Weilhammer, J.
Weingarten, C. Weiss, T. Wengler, N. Wermes, M.
Yamouni, M. Zavrtanik
PII:
S0168-9002(15)01150-X
DOI:
http://dx.doi.org/10.1016/j.nima.2015.09.079
Reference:
NIMA58092
To appear in:
Nuclear Inst. and Methods in Physics Research, A
Received date: 24 June 2015
Revised date:
11 September 2015
Accepted date: 16 September 2015
Cite this article as: M. Artuso, F. Bachmair, L. Bäni, M. Bartosik, J. Beacham,
V. Bellini, V. Belyaev, B. Bentele, E. Berdermann, P. Bergonzo, A. Bes, J-M.
Brom, M. Bruzzi, M. Cerv, C. Chau, G. Chiodini, D. Chren, V. Cindro, G.
Claus, J. Collot, S. Costa, J. Cumalat, A. Dabrowski, R. D'Alessandro, W. de
Boer, B. Dehning, D. Dobos, M. Dünser, V. Eremin, R. Eusebi, G. Forcolin, J.
Forneris, H. Frais-Kölbl, K.K. Gan, M. Gastal, M. Goffe, J. Goldstein, A.
Golubev, L. Gonella, A. Gorišek, L. Graber, E. Grigoriev, J. Grosse-Knetter, B.
Gui, M. Guthoff, I. Haughton, D. Hidas, D. Hits, M. Hoeferkamp, T. Hofmann,
J. Hosslet, J-Y. Hostachy, F. Hügging, H. Jansen, J. Janssen, H. Kagan, K.
Kanxheri, G. Kasieczka, R. Kass, F. Kassel, M. Kis, G. Kramberger, S.
Kuleshov, A. Lacoste, S. Lagomarsino, A. Lo Giudice, C. Maazouzi, I. Mandic,
C. Mathieu, N. McFadden, G. McGoldrick, M. Menichelli, M. Mikuž, A.
Morozzi, J. Moss, R. Mountain, S. Murphy, A. Oh, P. Olivero, G. Parrini, D.
Passeri, M. Pauluzzi, H. Pernegger, R. Perrino, F. Picollo, M. Pomorski, R.
Potenza, A. Quadt, A. Re, G. Riley, S. Roe, M. Sapinski, M. Scaringella, S.
Schnetzer, T. Schreiner, S. Sciortino, A. Scorzoni, S. Seidel, L. Servoli, A.
Sfyrla, G. Shimchuk, D.S. Smith, B. Sopko, V. Sopko, S. Spagnolo, S. Spanier,
K. Stenson, R. Stone, C. Sutera, A. Taylor, M. Traeger, D. Tromson, W.
Trischuk, C. Tuve, L. Uplegger, J. Velthuis, N. Venturi, E. Vittone, S. Wagner,
R. Wallny, J.C. Wang, P. Weilhammer, J. Weingarten, C. Weiss, T. Wengler, N.
Wermes, M. Yamouni and M. Zavrtanik, A 3D Diamond Detector for Particle
Tr a c k i ng ,
Nuclear
Inst.
and
Methods
in
Physics
Research,
A,
http://dx.doi.org/10.1016/j.nima.2015.09.079
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A 3D Diamond Detector for Particle Tracking
M. Artusov, F. Bachmairz, L. B¨aniz, M. Bartosikc, J. Beachamo, V. Bellinib, V. Belyaevn, B. Benteleu, E. Berdermanng, P. Bergonzom, A. Besad, J-M. Bromi, M. Bruzzie, M. Cervc, C. Chaur, G. Chiodiniac, D. Chrent, V. Cindrok, G. Clausi, J. Collotad,
S. Costab, J. Cumalatu, A. Dabrowskic, R. D’Alessandroe, W. de Boerl, B. Dehningc, D. Dobosc, M. D¨unserz, V. Ereminh, R. Eusebiaa, G. Forcolinx, J. Fornerisq, H. Frais-K¨olbld, K.K. Gano, M. Gastalc, M. Goffei, J. Goldsteins, A. Golubevj, L. Gonellaa,
A. Goriˇsekk, L. Grabery,∗, E. Grigorievj, J. Grosse-Knettery, B. Guio, M. Guthoffc, I. Haughtonx, D. Hidasp, D. Hitsz, M. Hoeferkampw, T. Hofmannc, J. Hossleti, J-Y. Hostachyad, F. H¨ugginga, H. Jansenc, J. Janssena, H. Kagano, K. Kanxheriae, G. Kasieczkaz, R. Kasso, F. Kassell, M. Kisg, G. Krambergerk, S. Kuleshovj, A. Lacostead, S. Lagomarsinoe, A. Lo Giudiceq, C. Maazouzii, I. Mandick, C. Mathieui, N. McFaddenw, G. McGoldrickr, M. Menichelliae, M. Mikuˇzk, A. Morozziae, J. Mosso, R. Mountainv, S. Murphyx, A. Ohx, P. Oliveroq, G. Parrinie, D. Passeriae, M. Pauluzziae, H. Perneggerc, R. Perrinoac, F. Picolloq, M. Pomorskim, R. Potenzab, A. Quadty, A. Req, G. Rileyab, S. Roec, M. Sapinskic, M. Scaringellae, S. Schnetzerp, T. Schreinerd, S. Sciortinoe, A. Scorzoniae, S. Seidelw, L. Servoliae, A. Sfyrlac, G. Shimchukj, D.S. Smitho, B. Sopkot, V. Sopkot, S. Spagnoloac,
S. Spanierab, K. Stensonu, R. Stonep, C. Suterab, A. Taylorw, M. Traegerg, D. Tromsonm, W. Trischukr, C. Tuveb, L. Upleggerf, J. Velthuiss, N. Venturir, E. Vittoneq, S. Wagneru, R. Wallnyz, J.C. Wangv, P. Weilhammerc, J. Weingarteny, C. Weissc,
T. Wenglerc, N. Wermesa, M. Yamouniad, M. Zavrtanikk
aUniversit¨at Bonn, Bonn, Germany bINFN/University of Catania, Catania, Italy
cCERN, Geneva, Switzerland dFWT, Wiener Neustadt, Austria eINFN/University of Florence, Florence, Italy
fFNAL, Batavia, USA gGSI, Darmstadt, Germany hIoffe Institute, St. Petersburg, Russia
iIPHC, Strasbourg, France jITEP, Moscow, Russia kJoˇzef Stefan Institute, Ljubljana, Slovenia lUniversit¨at Karlsruhe, Karlsruhe, Germany mCEA-LIST Technologies Avancees, Saclay, France
nMEPHI Institute, Moscow, Russia oThe Ohio State University, Columbus, OH, USA
pRutgers University, Piscataway, NJ, USA qUniversity of Torino, Torino, Italy rUniversity of Toronto, Toronto, ON, Canada
sUniversity of Bristol, Bristol, UK tCzech Technical Univ., Prague, Czech Republic
uUniversity of Colorado, Boulder, CO, USA vSyracuse University, Syracuse, NY, USA wUniversity of New Mexico, Albuquerque, NM, USA
xUniversity of Manchester, Manchester, UK yUniversit¨at G¨ottingen, G¨ottingen, Germany
zETH Z¨urich, Z¨urich, Switzerland aaTexas A&M, College Park Station, TX, USA abUniversity of Tennessee, Knoxville, TN, USA
acINFN-Lecce, Lecce, Italy adLPSC-Grenoble, Grenoble, France
aeINFN-Perugia, Perugia, Italy
Abstract
In the present study, results towards the development of a 3D diamond sensor are presented. Conductive channels are produced inside the sensor bulk using a femtosecond laser. This electrode geometry allows full charge collection even for low quality diamond sensors. Results from testbeam show that charge is collected by these electrodes. In order to understand the channel growth parameters, with the goal of producing low resistivity channels, the conductive channels produced with a different laser setup are evaluated by Raman spectroscopy.
Keywords: Tracking detectors, Solid State Detectors, CVD diamond
1. Introduction
1
Diamond sensors are radiation tolerant enough to be used in
2
the innermost layer of a future tracking detector at HL-LHC [1].
3
One challenge, when using diamond as a sensor material for
4
such a detector, is to improve the charge collection efficiency.
5
As trapping of charges is present even in unirradiated diamond,
6
a figure of merit is the charge collection distance (CCD),
7
i.e. the distance an electron-hole pair separates before the
8
charge carriers are trapped.
9 10
In order to collect the full charge from a sensor, the distance
11
between the electrodes has to be smaller than the CCD. For
12
planar electrodes, i.e. electrodes on the surface of the sensor,
13
this distance equals its thickness. Using electrodes which
14
penetrate the sample, so called 3D electrodes, decouples their
15
spacing from the thickness. To produce these electrodes in
16
a diamond sensor a phase change induced by a femtosecond
17
laser is used [2]. The diamond lattice is thereby transformed
18
into a combination of diamond-like carbon, amorphous carbon
19
and graphite, which is conductive. Continuous channels are
20
produced by moving the focal plane of the laser from the back
21
to the front side [3].
22 23
Another advantage of the 3D electrode geometry is the lower
24
bias voltage for the same electric field compared to planar
25
electrodes. This also allows a faster charge collection. Due to
26
these properties, 3D electrodes allow the use of less expensive
27
low CCD diamonds, while still obtaining the full signal.
28 29
In this paper in Section 2 testbeam results with a 3D diamond
30
sample are presented and Section 3 shows Raman spectra and
31
their interpretation of the conductive channels.
32
2. Testbeam results
33
A single crystalline (scCVD) diamond sample of electronic
34
grade with a thickness of 440μm and a size of 4.7 × 4.7 mm2
35
was used [4]. In this sample a total of 219 channels were grown
36
using a Coherent Libra Ti-Sapphire femto-second laser with a
37
wavelength of 800 nm. The laser was pulsed at 1 kHz with a
38
pulse duration of 100 fs. The beam was focused to a spot size
39
of about 4μm with an energy density of 2 J cm−2. The diamond
40
sample was mounted on a 3-axis motorised stage and moved
41
in the direction of the beam with a velocity of 20μm s−1with
42
respect to the laser.
43 44
The diamond sample was metallised using the mask shown
45
in Figure 1. It is divided into three parts to allow testing of the
46
influence of the metallisation and the conductive channels on
47
the charge collection on the same sample. One part is a planar
48
strip detector with a pitch of 50μm, which allows comparison
49
with traditional planar electrode sensors. The conductive
50
∗Corresponding author
Email address: lgraber@uni-goettingen.de(L. Graber)
Figure 1: Mask for the metallisation of the diamond sample [4]. It is divided into three parts. On the right a strip structure to connect all conductive chan-nels (“3D detector”), which is repeated in the middle but without conductive channels underneath (“3D phantom”) and on the left a planar strip detector.
channels of the 3D part are organised in cells with a size of
51
150× 150 μm2, each with a readout channel in the centre of
52
the cell and four bias channels in the corners. These cells were
53
connected column wise to a single readout. The metallisation
54
pattern for this structure is duplicated once on the sample, but
55
with no conductive channels underneath (“3D phantom”). This
56
allows the measurement of the influence of the metallisation
57
pattern on the charge collection.
58 59
The sample was read out by connecting each strip to a charge
60
sensitive amplifier channel of a VA2 chip [5]. A testbeam
61
with 120 GeV pions was performed at the H6 CERN-SPS
62
beam line. A silicon strip telescope, triggered by two external
63
scintillators, provided particle tracking information [6]. The
64
planar strip detector was biased with a voltage of 500 V (the
65
diamond sensor showed full charge collection for bias voltages
66
in excess of 450 V) and the two 3D structures with 25 V.
67 68
For each readout channel the initial pedestal and its width
69
(σ) was determined using the first 500 events. The pedestal
70
of later events was calculated using the 500 events directly
71
prior to the event, while excluding signal events (i.e. events
72
with more charge than 5σ). The pedestal and common mode
73
were subtracted for each channel. Only events with one track
74
were used in this analysis. The signal from the diamond was
75
calculated by summing up the signal from the three channels
76
closest to the predicted track position.
77 78
A negative signal response was observed for some channels
79
at values which exceed the pedestal width by far. A cut was
80
performed at−700 e which corresponds to 7.4σ of the pedestal
81
width. The predicted track position of these events are
pre-82
dominantly located near bias electrodes. These channels have
83
been identified as missing in resistance measurements. Missing
84
readout electrodes can be identified by the significantly reduced
85
signal measured in these cells.
86 87
For the analysis a fiducial region was defined on the 3D
88
Figure 2: Charge spectra from the 3D detector and from the strip detector [4]. The peak of the distribution is for the 3D detector at 13, 900 e and for the strip detector at 13, 800 e. The mean values are 15, 000 e and 15, 800 e for the 3D and for the strip detector, respectively.
detector which contains no missing readout channels and few
89
missing bias electrodes. Signals from the 3D detector show
90
a most probable charge of 13, 900 e compared to 4, 400 e for
91
signals from the 3D phantom. This shows that the conductive
92
channels do collect charges, as the influence of the metallisation
93
is the same in both regions. The signal from the planar strip part
94
has a most probable value of 13, 800 e as shown in Figure 2. It
95
operates at a much higher bias voltage where full charge
col-96
lection is expected for this diamond sample. This shows that
97
with the 3D design it is possible to collect the full charge while
98
applying a lower bias voltage.
99
3. Raman spectroscopy
100
A femtosecond laser is used to produce the conductive
101
channels in diamond. The focal plane of this laser is moved
102
from the back to the front of the sample. The reason for
103
this is that the product of the phase change absorbs the laser
104
radiation and thus prevents phase change of the diamond
105
material downstream of the laser. This results in very different
106
structures of the conductive channels on the surface of the
107
diamond, where the laser focus enters (“seed side”) or exits
108
(“exit side”) of the crystal.
109 110
On the seed side the conductive material is only irradiated by
111
the first few pulses of the femtosecond laser as further pulses
112
are absorbed by material grown upstream. This is not the case
113
on the exit side, where the material is exposed for many pulses,
114
which heat it up. This local heating results in a evaporation of
115
parts of the grown channel, leading to a crater like structure.
116
Such a crater can be disadvantageous for a good metal to
117
conductive channel contact on this side. It could happen, that
118
the crater is too narrow for the metal layer to reach the graphite
119
at its bottom. A metallisation from both sides is needed for the
120
application of the 3D diamond as a pixel detector.
121 122
Furthermore, in order to use it as a pixel detector, the
123
resistivity of the conductive channels has to be uniform and
124
low. The composition of the material after the phase change
125
can depend on several parameters of the laser, like wavelength,
126
pulse duration, and size of the focal plane. Most of these are
127
fixed for a given setup, so usually the only variable parameters
128
for an optimisation of the growth are the fluence of the beam
129
and the velocity of the focal plane through the diamond. For
130
production of a larger amount of 3D diamond sensors, which
131
could be e.g. for a tracking detector, a low production time
132
is crucial. To achieve this, generally more than one available
133
femtosecond laser is advantageous, but also femtosecond lasers
134
which are pulsed at a higher frequency. The difference of the
135
growth of conductive channels in single crystalline and lower
136
grade poly crystalline (pCVD) diamond should also be studied.
137 138
For these reasons, a total of 246 conductive channels were
139
grown in a pCVD diamond sample of 500μm thickness. These
140
channels were produced at Laser-Laboratorium G¨ottingen
141
e.V. using a Yb:YAG femtosecond laser with a wavelength
142
of 1043 nm. The pulse duration was 290 fs with a repetition
143
rate of 200 kHz. The diameter of the focal plane was about
144
1.6 μm. In order to determine the best growth parameters
145
with this setup, four power settings and four velocities of the
146
diamond with respect to the laser were tested. These values
147
covered a large parameter space, namely 10, 25, 60, 150 mW
148
for the power and 50, 200, 2000, 10000 μm s−1for the velocity.
149
For each combination of these two parameters, at least five
150
channels were produced. The success rate for a conductive
151
channel without any interruptions was determined by optical
152
inspection to be 88%.
153 154
In order to measure the influence of these parameters on the
155
phase change, especially on the exit side, Raman spectroscopy
156
was performed. The measurement of the Raman spectra was
157
performed using a laser with a wavelength of 440 nm and a
158
spot size of about 2μm. This is significantly smaller than the
159
diameter of the smallest conductive channel, which is about
160
4μm. Prior to the measurement of the conductive channels two
161
reference measurements were performed. The first
measure-162
ment, with the laser focused in a region where no conductive
163
channels are present in the diamond sample, yielded a narrow
164
peak at 1332 nm−1as expected for pure diamond. In the second
165
measurement a highly conductive graphite sample was used.
166
It showed two broad peaks of nearly the same amplitude at
167
approximately 1580 nm−1 and 1350 nm−1. These peaks are
168
called the g- and d-peak, respectively. The first one is attributed
169
to ordered graphite, the second one to unordered graphite [7].
170 171
In all spectra of the conductive channels a clear contribution
172
from graphite, indicated by the g- and d-peak, is visible,
173
although it varies in intensity. For almost all spectra, except
174
for a few with high energy and high velocity, a diamond peak
175
is noticeable. This peak strongly varies in intensity, being
176
suppressed for high energy and high velocity while being
177
50um/s , 10mW 200um/s , 10mW 2000um/s , 10mW 10000um/s , 10mW 50um/s , 25mW 200um/s , 25mW 2000um/s , 25mW 10000um/s , 25mW 50um/s , 60mW 200um/s , 60mW 2000um/s , 60mW 10000um/s , 60mW 50um/s , 150mW 200um/s , 150mW 2000um/s , 150mW 10000um/s , 150mW 50um/s , 60mW 200um/s , 60mW 2000um/s , 60mW 10000um/s , 60mW 50um/s , 150mW 200um/s , 150mW 2000um/s , 150mW ratio 0 10 20 30 40 50 60 70 2χ 0 200 400 600 800 1000 1200 1400 1600 1800
Figure 3: Ratio of the value of the diamond peak to the value of the g-peak. Results for individual channels are marked by a blue cross, the weighted mean for each setting is indicated by the green line. The red dotted line shows theχ2value for each setting (for a coloured version of the plot the reader is reffered to the web
version of this paper).
] -1 [cm λ 1/ 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 counts [a.u.] 200 400 600 800 1000 1200 1400 1600 Data Fit Diamond 1 D 2 D 1 G 2 G linear
Figure 4: Raman spectrum for the seed side of a channel grown at 60 mW and 2, 000 μm s−1. Individual contributions of the fitted functions are shown.
dominant for low energy or low velocity. In general, the
178
diamond contribution is more apparent on the exit side. This is
179
expected, as part of the material is evaporated, leaving behind
180
a crater-like structure.
181 182
To evaluate the spectra, they are fitted by a combination of
183
five Gaussian distributions and a linear function describing
184
the peaks and the background, as shown in Figure 4. Since
185
the diamond peak is very narrow and consists of roughly five
186
data points, the fit quality on this peak in the combined fit is
187
generally poor. Thus for the extraction of the diamond peak
188
value, an extra Gaussian fit in the region between 1327 nm−1
189
and 1340 nm−1is performed.
190 191
As a rough figure of merit for the quality of the channels,
192
the ratio of the height of the diamond peak to the height of the
193
g-peak is calculated. The result is shown in Figure 3. For low
194
energies of 10 mW and low velocities of 50μm s−1 the ratios
195
from the individual channels on the seed side are highly
fluc-196
tuating. This indicates, that the energy needed for the phase
197
transition is barely reached and only little conductive material
198
is created. For the seed side higher energies and velocities yield
199
all reasonable low ratios. On the exit side only channels grown
200
with a velocity of 2, 000 μm s−1or faster have enough
remain-201
ing graphite in the crater like structure to be measured with
Ra-202
man spectroscopy. Here for energies above 60 mW the diamond
203
contribution is fairly low.
204
4. Conclusion
205
Results from a testbeam of a scCVD diamond with 3D
elec-206
trodes show, that these channels do collect charges. This
tech-207
nique allows the full collection of the deposited charge even for
208
samples with a CCD lower than their thickness. The best
set-209
tings for a femtosecond laser setup have been investigated with
210
a pCVD diamond. Results show a systematic difference of the
211
structure of the conductive channels on the seed and exit side.
212
Acknowledgments
213
The conductive channels in the pCVD diamond were
pro-214
duced at Laser Laboratorium G¨ottingen e.V. The Raman
spec-215
troscopy was performed at Geowissenschaftliches Zentrum of
216
the University of G¨ottingen. This work was supported by the
217
German Federal Ministry of Science and Education, BMBF, via
218
the collaboration research center, BMBF-FSP 101, under
con-219
tract number 05H12MG1.
220
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221
Nucl. Instrum. Meth. A367 (1995) 207–211.
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[2] T.V. Kononenko, et al., Microstructuring of diamond bulk by IR
femtosec-223
ond laser pulses, Applied Physics A90 (2008) 645–651.
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[3] T.V. Kononenko, et al., Three-dimensional laser writing in diamond bulk,
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Diamond and Related Materials 20 (2011) 264–268.
226
[4] F. Bachmair, et al., A 3D diamond detector for particle tracking, Nucl.
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Instrum. Meth. A786 (2015) 97–104.
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[5] Integrated Detectors & Electronics AS, Data Sheet VA2 Readout Chip,
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Oslo, Norway, 2014.
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[6] C. Colledani, et al., A submicron precision silicon telescope for beam test
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purposes, Nucl. Instrum. Meth. A372 (1996) 379–384.
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[7] A.C. Ferrari, J. Robertson, Interpretation of Raman spectra of disordered
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