Solid State Detectors- 6

T. Bowcock

2

Schedule

1 Position Sensors

2 Principles of Operation of Solid State

Detectors

3 Techniques for High Performance Operation

4 Environmental Design

5 Measurement of time

6 New Detector Technologies

3

New Technologies

• Si developments– Oxygenated Si– p-type Si

• Diamond• Cryogenic Si• Deep Sub-Micron Processing• Nanotechnologies• Physics

4

Oxygenated Si

• Introduce oxygen into the wafer before fabrication

• O2 permeated by diffusion– 1100 to 1200 C

• Performance• Manufacturer

– e.g. Micron

• Furnace

5

Oxygenated Si

6

Oxygenated Si

Trying to unfold the performance

7

Oxygenated Si

• Performance with diodes superb– factor 2

improvement

• Strip performance seems to be about 20% better

8

p-type Si

• As irradiated n-type– use n-strips

• Advantages– single sided

processing– detector does not

invert

• Slightly degraded performance

9

P-type Si

10

Cryogenic Operation

• Lazarus Effect– cool detector down it appears to repair itelf– standard technology but cold– diodes

• Strip detectors irradiated while cold– double sided– monitor both p and n side

11

Cryogenic Operation

• DELPHI detectors

12

Cryogenic Operation

13

Cryogenic operation

14

Cryogenic Operation

15

Cryogenic Operation

• Lazarus effect could be observed– charge injection into a reverse biased

detector– filling traps with electrons– uncontrolled– fine tuned with temperature&frequency

• Is there a way to control this?

16

Diamond

• Use Diamond as a material– radiation hard– cheap(!)– large area

17

Diamond Formation

• Chemical Vapour Deposition(CVD)

substrate

Small crystals of order microns

Larger crystals 20-30 microns

18

Diamond Charge

• Charge produced by ionization

• Traps– interstitials– vacancies– shallow and deep

• Charge Collection Distance

19

Diamond Performance

20

Diamond Performance

21

Diamond

• Very high fluences– at current radiation levels does not out

perform Si– limited charge collection distance

• small crystals?

22

Summary of Current New Technologies

• Si reaching maturity– extension such as O2 fine tune

performance

• New generation of materials (e.g. diamond) can be used under extreme conditions

23

Speculative Technology

• Plastic diodes

• New Si processing

24

Organic diodes

• “In 1989 it was discovered that a conjugated polymer, poly(1,4-phenylenevinlyene) (PPV), could be used as a light emitting layer in LEDs. This discovery has wide ranging commercial possibilities, e.g., the preparation of lightweight, large, multicoloured, flat panel displays for televisions and computer screens is now a realistic possibility”. (D. Burn).

PPV

25

Polymer Diodes

• A simple LED consists of a polymer sandwiched between two metal electrodes.

• The electrons and holes charges move in opposite directions and if they end up on the same polymer chain then they can form a singlet excited state which can decay and emit light

• The colour of the light is dependent on the HOMO-LUMO energy gap.

26

Polymer diodes

• TV screens– very commercial

• If becomes viable perhaps we can benefit

• R&D– flexible – robust– cheap

27

Deep Sub-Micron Processing

• Current generation of processing at 0.16 level or better.

• CMOS designs– intrinsically

radiation hard– bulk effects vanish

• Better readout chips– higher density– improved VLSI– low cost– high radiation– pixel detectors(!)

28

Deep Sub-Micron

• Large areas

• High resolution

• What we need for large area high quality production of detectors

• COST inhibitive at the moment– CCD large scale high resolution

29

Nanotechnology

• Look and manufacture things on the sub-nm scale

• Si(111) surface• GaAs

30

Nanotechnology

• A 200 Å x 200 Å constant current STM image of an alpha-Fe2O3(0001) surface . This image shows two types of island, which are ordered, forming a hexagonal superlattice. The unit cell of the superlattice has a characteristic dimension of 40 ± 5 Å and is rotated by 30 degrees from the alpha-Fe2O3(0001) lattice.

31

Nanotechnology

• If we could find a way of recording mip through a material– ultimate 0.1 nm scale detector– electronic (slow!) r/o

32

Physics

• From applied physics point of view all these technologies are very interesting

• How applicable are they to particle physics?• Ultimate measurement as resolution

improves

33

Particle Physics

• Detector resolution– Vertex

• topology of vertex • decay lengths

– Tracking • momentum of particles• usually large volume gas detector

34

Vertex Finding

• Heavy quarks decay quickly– b in about 1ps (mm in current machines)– t in fs or less (where primary

hadronisation occurs)

• Increasing resolution would improve our separation of b-quarks from the primary collision – decrease luminosity

35

Vertex Finding

If you have good resolution you don’t need to get so close

36

Vertex Finding

• In telescope– limited by mechanical accuracy – thermal expansion etc

• Practical limit to resolution JUST from these considerations O(1 micron)

• Multiple Scattering

37

Multiple Scattering

• Multiple Coulomb Scattering

• About 1mr /p for 300 microns of Si

1 micron at 10GeV

1 cm

38

Multiple Scattering

• Angles give mass resolution for hadronic decays

• Already ms limited in many cases– slow pions < 0.5 GeV/c

• HEP seems to be less interested in hadronic decays masses than decay rates– CPT not approachable by this method

39

Vertex Finding

• For fast (active r/o) devices we are probably within a factor 10 of limit with current technology

• Topology of the decays– thin retaining signal– surface nano-readout– alignment?

40

Tracking

• High resolution detectors useful– detectors have large gas volumes– large volumes make calorimetry

expensive

• Momentum measurement

41

Momentum measurement

R

h

d

4hR=d2

P=0.3BR

42

Momentum Measurement

• Measurement of sagitta is key– multiple scattering counts– Si usually not used– Time Projection Chamber (?)

43

Summary (New Technology)

• We are close to performance limits (for what we need) … micron level precision active detectors

• New Technology gives performance in extreme cases– e.g. radiation– extreme resolution– cost

44

Conclusion

• Detectors have developed in 100yrs

• Understood basic solid state detectors

• Research that is being followed

• New Horizons/Technologyes

• Up to you to have the good ideas– and find the physics that needs it