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Below and using the index to the left, you can find summarised part of the silicon detector activity in the Physics Department of the University of Liverpool. You can also find my personal pages here.
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| Silicon detector studies
This page summarises the work done in the silicon detector laboratory of the HEP Group (University of Liverpool - Department of Physics) |
| The silicon detectors will provide the main tracking capability for the future experiments in high-energy physics. In most of these experiments they will have to withstand a harsh radiation environment. The survival of the detectors to the severe radiation fluences they will receive is a challenge for the detector technology. We are involved in the development of the sensors for several of the major experiments that will take place in CERN-LHC (ATLAS, LHCb) and FERMILAB (CDF). In this page I have collected several results concerning the study of silicon detectors mainly on the subject of their radiation hardness. |
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I've conceived the high temperature diffusion technique to introduce
high concentrations of oxygen into silicon wafers. This development was
done in the frame of RD48 collaboration. It can be used for other fast
diffusing element in silicon. You find
here the description of this technique.
Also look in: http://rd48.web.cern.ch/RD48/, Technical Reports page, ROSE/TN/99-1. You can find further details in Chapter 5 and Appendix B of my PhD thesis. |
Large area and miniature segmented detectors
In the development of silicon microstrip detectors for high energy physics applications the Liverpool laboratory clearly established the advantage of reading out finely segmented devices from the n-type implants. Silicon detectors made with n-type bulk silicon undergo space charge sign inversion after being irradiated with hadron to a dose of a few 1013 cm-2 The standard diode structure for segmented detectors used in high energy physics is p-strips implanted into a lightly doped n-type substrate. With this geometry, after type-inversion, the high electric field is on the opposite side to the read-out strips, resulting in a reduced charge collection vs bias (CCE(V)) at low voltages. The CCE(V) can be improved by segmenting and reading out the n-side of the detector (n-in-n geometry). Very good performance after irradiation has been achieved with this geometry. An example of the advantages of this geometry is shown here. The n-side read-out concept is now widely accepted. The most exposed silicon detectors of the LHC experiments (ATLAS and CMS pixels and LHCb-VELO microstrips) all use n-side read-out.
P-type silicon detectors
The limitation with the n-in-n devices is the higher processing cost, and, to a lesser extent, that the junction side (and the high electric field) is on the opposite side before irradiation. Both the migration of the junction after type inversion and the extra cost due to the double-sided processing can be avoided by using a p-type bulk substrate. Concerning the CCE(V) properties as a function of the cumulated fluence, an improvement similar to the n-in-n read-out was expected with p-type substrates. To investigate this issue we first produced ATLAS SCT geometry, p-type substrate detectos with p-stop interstrip isolation. The production was successful and proved the feasibility and the improvements of this solution. The irradiation fluence was up to LHC tracker levels (~ 4. 1014 p cm-2). To further study the radiation hardness of these detectors to super-LHC levels we produced miniature n-in-p capacitively coupled, polysilicon biassed microstrip detectors (1x1 cm-2, 100 strips). These miniature devices allowed us to investigate the charge collection properties up to 7.5 1015 p cm-2. I report here the extremely positive results we have obtained.
Last modified: 18/08/2008
