Accession Number:

ADA393575

Title:

Nuclear Radiation-Induced Dimensional Changes in Borosilicate Glass Substrates

Descriptive Note:

Thesis

Corporate Author:

MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF MATERIALS SCIENCE AND ENGINEERING

Personal Author(s):

Report Date:

2001-08-10

Pagination or Media Count:

112.0

Abstract:

A study was made of radiation-induced dimensional changes in PyrexRegistered and Hoya SD-2Registered glasses. These glasses are used as substrates for MEMS devices employing silicon oscillating beams, and changes in substrate dimension can compromise device performance. Silicon MEMS strain gauges mounted on glass substrates were exposed to gamma doses up to 385 Mrad. The device-substrate differential strain thus measured corresponds to an expansion in the glass following a linear trend with dose of about 5 -4 x 10exp -15 rad and 4.5 -0.2 x 10 exp -14 rad for Pyrex and Hoya SD-2, respectively. Separate glass samples were irradiated with a neutron fluence composed primarily of thermal neutrons, and a floatation technique was employed to measure the resulting density changes in the glasses alone. Transport of Ions in Matter TRIM calculations were performed to relate fast 1MeV neutron atomic displacement damage to that from boron thermal neutron capture events, and measured density changes in the glass samples were thus proportionally attributed to thermal and fast neutron fluences. Maximum neutron fluences received by glass samples were estimated at 4 x lOexp 16nsq cm thermal and 6 x 10exp 14nsq cm fast. The glasses irradiated with thermal neutrons were found to exhibit linear compaction at a rate of -2.8x10exp -2O per nsq cm for Pyrex and -1.0xexp 10-21 per nsq cm for Hoya SD-2. For fast neutron fluence, strain rate per nsq cm was also linear -6.1x10exp -21 for Pyrex and -7.9x10exp -22 for Hoya SD-2. The gamma irradiation strain gauge results cannot be explained by the radiation-induced compaction previously reported for Pyrex, and are thought to result from either changes in glass radiation response caused by the anodic bonding process used to make the MEMS strain gauges or from radiation-assisted creep of the strain gauge anchors. The neutron irradiation results for Pyrex show good agreement with those of previous studiesc

Subject Categories:

  • Electrical and Electronic Equipment
  • Ceramics, Refractories and Glass

Distribution Statement:

APPROVED FOR PUBLIC RELEASE