Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Non-dispersive infrared gas analyzer for vapor density measurements of a carbonyl-containing organometallic cobalt precursor



James E. Maslar, William A. Kimes, Brent A. Sperling, Ravindra Kanjolia


A non-dispersive infrared (NDIR) gas analyzer was demonstrated for measuring the vapor-phase density of the carbonyl-containing organometallic cobalt precursor μ2-η2-(tBu- acetylene) dicobalthexacarbonyl (CCTBA). This sensor was based on direct absorption by CCTBA vapor in the C≡O stretching spectral region and utilized a stable, broadband infrared filament source, an optical chopper to modulate the source, a bandpass filter for wavelength isolation, and a cryogenic InSb detector. The optical system was calibrated self-consistently by selecting a calibration factor to convert CCTBA absorbance to a partial pressure that, when used to calculate CCTBA flow rate and CCTBA mass removed from the ampoule, resulted in an optically-determined mass that was equal to a gravimetrically-determined mass. In situ FT-IR spectroscopy was performed simultaneously with the NDIR gas analyzer measurements in order to characterize potential interferences. Interference due to CO evolution from CCTBA was found to be small under the flow conditions employed here. A CCTBA minimum detectable molecular density as low as  3 x 1013 cm 3 was calculated with no signal averaging and for a sampling rate of 200 Hz. While this NDIR gas analyzer was specifically tested for CCTBA, it is suitable for characterizing the vapor delivery of a wide range of carbonyl-containing precursors.
Applied Spectroscopy


ALD, atomic layer deposition, CCTBA, CVD, chemical vapor deposition, infrared absorption, cobalt, non-dispersive infrared gas analyzer, NDIR, (tBu-acetylene) dicobalthexacarbonyl


Maslar, J. , Kimes, W. , Sperling, B. and Kanjolia, R. (2017), Non-dispersive infrared gas analyzer for vapor density measurements of a carbonyl-containing organometallic cobalt precursor, Applied Spectroscopy, [online], (Accessed July 22, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created December 1, 2017, Updated November 10, 2018