Daniel A Moreno

US Patent:

58346279, Nov 10, 1998

Filed:

Dec 17, 1996

Appl. No.:

8/766142

Inventors:

Antonio J. Ricco - Albuquerque NM
Robert C. Hughes - Cedar Crest NM
James H. Smith - Albuquerque NM
Daniel J. Moreno - Albuquerque NM
Ronald P. Manginell - Albuquerque NM
Stephen D. Senturia - Brookline MA
Robert J. Huber - Bountiful UT

Assignee:

Sandia Corporation - Albuquerque NM

International Classification:

G01N 700

US Classification:

73 2331

Abstract:

A combustible gas sensor that uses a resistively heated, noble metal-coated, micromachined polycrystalline Si filament to calorimetrically detect the presence and concentration of combustible gases. The filaments tested to date are 2. mu. m thick. times. 10. mu. m wide. times. 100, 250, 500, or 1000. mu. m-long polycrystalline Si; some are overcoated with a 0. 25. mu. m-thick protective CVD Si. sub. 3 N. sub. 4 layer. A thin catalytic Pt film was deposited by CVD from the precursor Pt(acac). sub. 2 onto microfilaments resistively heated to approximately 500. degree. C. ; Pt deposits only on the hot filament. Using a constant-resistance-mode feedback circuit, Pt-coated filaments operating at ca. 300. degree. C. (35 mW input power) respond linearly, in terms of the change in supply current required to maintain constant resistance (temperature), to H. sub. 2 concentrations between 100 ppm and 1% in an 80/20 N. sub. 2 /O. sub. 2 mixture.