Passivation of HPGe Detectors at LNL-INFN

Speaker: Gianluigi MaggioniMaterials & Detectors Laboratory (LNL-INFN)

Scientific Manager: Prof. Gianantonio Della Mea

Staff2 Ph.D. in Materials Engineering1 Ph.D. in Chemistry1 Degree in Materials Science3 Engineers (in Electronics and Materials Science)1 Technician3 Ph.D. Students in Physics, Materials Science and Engineering

The activities of the Lab are devoted to the:1. Synthesis of new materials (thin and thick films)2. Modification of materials3. Characterization of the physical / chemical properties of materials

The research activities are mainly funded by INFN (about 3 experiments per year starting from nineties in the framework of V INFN Commitee) by inter-University MIUR research programs, by other National and International Research Institutions.

1. Synthesis of MaterialsPVD Facilities

6 Sputtering deposition apparatuses

2 High Vacuum Evaporation chambers

1 Glow-Discharge-induced Sublimation apparatus

Chemical Techniques

Spin Coating

Sol-Gel

Tape Casting

Solvent Casting

Liquid Phase Deposition

3. Characterization of the physical / chemical properties of materials

Composition (Nuclear Techniques: RBS, ERDA, NRA, IBIL, PIXE)

Morphology (AFM, SEM)

Electrical Properties (resistivity, surface resistance, dielectric breakdown field)

Mechanical Properties (Micro Scratch Test, Nano Indentation, Micro Indentation)

Chemical Structure (FT-IR Analysis)

Optical Properties (UV-visible spectrophotometry)

Previous experience in Germanium Detectors Technology

Collaboration project with EG&G Ortec “Advanced passivating techniques for the development of ruggedized HPGe detectors” (1997-1999)

Aim: an alternative to the detector encapsulation procedure (complex, expensive,...)

Passivation techniques:• deposition of oxides layers by liquid phase deposition (LPD)

These techniques were not adopted because they could not be easily applied to industrial production (according to EG&G Ortec)

New passivation technique:

Vacuum Deposition of a Polymer Layer

Polymer Deposition Apparatus

New passivation technique:

Vacuum Deposition of a Polymer Layer

Polymer Deposition Apparatus

New passivation technique:

Vacuum Deposition of a Polymer Layer

HPGe Detector

New passivation technique:

Vacuum Deposition of a Polymer Layer

• Vacuum Deposition Process (no solvent)

• Room Temperature Deposition Process

• Post-deposition curing is not required

• Very clean deposition process (compatibility with clean room operations)

• Detectors with complex shape can be coated

• Very low permeability to moisture, oxygen, … (barrier properties)

• Electrically insulating material ( > 1016 Ohm cm)

• High thermal resistance (Tg 250-400°C)

• The coated detector can be handled

• Layer thickness: 1 to 50 m

• Radiation hardness