Measurements on Single and Poly Crystal CVD Diamond Sensors

Christian Grah, DesyFCAL Workshop12-13 FebruaryCracow

FCAL Workshop Cracow, 12-13 Feb 2006

C.Grah: Diamond Sensors 2

Low dose rate irradiation of polycrystalline CVD sensors, measure the Charge Collection Distance, CCD vs dose• E64

• Desy7

Single crystal diamond• IV

• Individual spectra

• CCD vs HV/time

Summary & outlook

Contents

FCAL Workshop Cracow, 12-13 Feb 2006

C.Grah: Diamond Sensors 3

Low Dose Rate Irradiation Usually irradiation in our laboratory is done by:

1. Irradiation with closest possible distance between source and sensor (typically 2.6 cm) to achieve high dose rate.

2. Measure the CCD of the sensor in regular time intervals with a reasonable distance to prevent a high double hit rate (typically 7.5cm).

This enables for reproducible measurements on a timescale of several days to get into the 100 Gy range of accumulated dose.

BUT: need of an operator

LOW DOSE RATE IRRADIATION: => automatic CCD measurement at low dose rate, but needs much more time.

Did this at the time of the TAU workshop 2005.

FCAL Workshop Cracow, 12-13 Feb 2006

C.Grah: Diamond Sensors 4

CCD MeasurementUse the high

energetic part of a Sr90-β- source => MIP spectrum.

Δt = 30min

FCAL Workshop Cracow, 12-13 Feb 2006

C.Grah: Diamond Sensors 5

E64 Irradiations

29.8. – 5.9. (~7d) 6.9. – 9.11. (~64d)

Have done 2 irradiation periods with different dose rates:

FCAL Workshop Cracow, 12-13 Feb 2006

C.Grah: Diamond Sensors 6

Desy7 and Desy8 Got these two new samples in Nov. 06. The samples are 300 μm thick and 12x12 mm in size. The metallization is 10x10 mm in size divided into 4

pads on one side. 100 nm Ti + 200 nm Pt + 500 nm Au. Material selection was with focus on avoiding micro

cracks.

FCAL Workshop Cracow, 12-13 Feb 2006

C.Grah: Diamond Sensors 7

Desy7 and Desy8 (cont.)

pCVD Diamonds from Freiburg (Fraunhofer IAF)

Main issue from former samples:• micro cracks• IV behavior• CCD performance• CCD vs irradiation

Large part of the measurements were presented by K. Afanaciev. Much better performance than earlier samples.

Issue of signal decreasing with time.

FAP7 series

FCAL Workshop Cracow, 12-13 Feb 2006

C.Grah: Diamond Sensors 8

Spectra of Desy7

Shortly after switching thehigh voltage a large signal is measured.

Took pedestal as determinedby the early measurementsand fixed it for the rest.

FCAL Workshop Cracow, 12-13 Feb 2006

C.Grah: Diamond Sensors 9

Low Dose Rate Result

switching voltage

22.12.05- 11.1.06

Stable signal!

FCAL Workshop Cracow, 12-13 Feb 2006

C.Grah: Diamond Sensors 10

BDS7 - IV Started to investigate a sCVD Diamond. Got the sample (BDS7) in December from the GSI

Darmstadt. 5 x 5 x 0.318 mm3 ;

Cr(50 nm)Au (100 nm) or Ti(30nm)Pt(50nm)Au(100nm)

known “breakthrough”

FCAL Workshop Cracow, 12-13 Feb 2006

C.Grah: Diamond Sensors 11

Mip signal of BDS7

FCAL Workshop Cracow, 12-13 Feb 2006

C.Grah: Diamond Sensors 12

BDS7 CCD

The single crystal diamond shows a high (100%) and stable (t) signal even at low E-field.

thickness

FCAL Workshop Cracow, 12-13 Feb 2006

C.Grah: Diamond Sensors 13

SummaryHave tested sensors from E6 and IAF

(Freiburg) up to highest doses so far in our lab (>250 Gy).

Desy7 and Desy8 show a small but stable signal and did not show any microcrack related problem.

Started to test a single crystal diamond (sCVD) from E6.

Superior efficiency at low E-field and very stable behaviour of the sCVD sample.

FCAL Workshop Cracow, 12-13 Feb 2006

C.Grah: Diamond Sensors 14

Outlook We will get pCVD samples back from Freiburg

with annealed (10min@500°C) metallization. Expected this week.

Waiting for new thin samples from Freiburg from a dedicated wafer with reduced nitrogen concentration during growth.

We will have a testbeam period (end of April) at the TU Darmstadt DALINAC (10MeV and ~15Gy/s) and will investigate high dose behavior of diamonds.

sCVD diamonds are interesting but they are not (yet) available on waferlevel. Will follow the development of this technology.