Paper VT-WeM13
History of Very Thick Film and Bulk Sample Group IIIB, IVB, VB and Rare Earth Materials for Various Vacuum Applications

Wednesday, November 1, 2017, 12:00 pm, Room 7 & 8

History of Very Thick Film and Bulk Sample Group IIIB, IVB and Rare Earth

Materials for Various Vacuum Applications

James L. Provo ^(a

Consultant, J.L. Provo Consulting, Trinity, FL 34655-7179

Thick occluder films of hydride materials are extremely hard to produce without

flaking or cracking. This paper discusses methods of how to prepare thick films

and bulk samples (i.e., rods and wires) for many applications including accelerator

research for cancer therapy, intense neutron source, and particle-beam fusion

diagnostic beam focusing studies. These thick films ~ ( ≥ 5,000 to 15,000 nm

thick) of various hydrides are sensitive to oxidation and are easily contaminated by

improper handling. They must be specially prepared to reduce internal stresses due

to temperature variations during processing, and stresses due to hydriding and to

substrate configuration ( i.e., curved surfaces). This paper will discuss techniques

developed at the General Electric Neutron Devices Department (GEND), in Largo, FL,

in the mid-1970's to the late 1990's to produce stress free and thus flaking and crack

free samples of thick films and bulk samples. Items studied include, Er, Sc, and Ti

thick film hydrides on a Cr underlay, on various substrates, bulk rod samples (0.635

cm O.D. by 2.54 cm long) for basic material heat capacity and thermal diffusivity

studies as a function of hydride loading, Nb and V wires 10 and 20 mil O.D. by 5.08

cm long in bundles of ~30 wires for neutron vibration spectra studies and 20 mil O.D.

by 1.27 cm long Ti wires for mass spectrometer calibration studies. Film samples were

prepared by standard E-beam evaporation techniques and then non air-exposure loaded.

Bulk samples were cleaned, weighed, and then loaded with a Sievert's precise gas

quantity loading system. Special processing to accomplish flake and crack free samples,

included heating sample substrates for thick films to 450°C, evaporating at a controlled

rate of 10 nm/min.,which takes ~ 8.3 hrs. for 5,000 nm films and ~25 hrs. for 15,000

nm films, followed by non-exposure loading (i.e., leaking D₂ or T₂ gas into the loader) at a

rate of 1Torr/hr. until 50 Torr is reached, which will take ~2-days, holding at temperature

and pressure for ~ 8hrs, then cooling down at a rate of 1°C/ min.from 450°C to room

temperature. Er films are cooled to ~ 320°C, then gas is removed to the source bed to

prevent trihydride formation, before cooling to ~ (25°), which will take ~ 7.5hrs. Using

the process described, very successful results were obtained.

^* Formerly, Principle Member of the Technical Staff at Sandia National Laboratories,

Albuquerque, New Mexico 87185 (Retired); electronic mail: jlprovo@verizon.net.