Deep Ultraviolet Measurements

McPherson, Inc.

Deep and vacuum ultraviolet measurements have never been better, or easier.

Ultraviolet (UV) spectrophotometry has a well-deserved niche. Many UV-Vis instruments claim to work to the deep UV. Few instruments optimize for, or cater to, the 120 to 400 nm region. Development and manufacture of ultraviolet lasers, optics, crystalline materials, and resonance Raman instruments, as well as basic research, require a broadly useful instrument for analysis, characterization, and test. Enter McPherson's Vacuum Ultraviolet Analytical Spectrophotometer (VUVAS.)

The McPherson VUVAS instrument meets the requirements of deep and vacuum ultraviolet analysis in the 120 to 400 nm range. From clean, particulate free and tight, purge or vacuum capable enclosure, to UV enhanced optics, sources, detectors, and computer optimized optical system. All VUVAS elements improve analytical results and simplify measurement tasks for the user.

The VUVAS spectrophotometer works with gas or liquid sample cells. Most users employ coated substrates for transmission measurements. A three-position sample holder is standard. Cryogenic single-sample mounts, and raster-mapping attachments for large samples, are available as specials. The VUVAS also allows users to measure reflectance and easily alter angle of incidence to the sample. The detector is adjustable. It can maintain theta/2-theta geometry for specular reflectance measurements, or deviate from this, to measure scatter or dispersive samples.

The VUVAS design delivers absolute measurements. A single detector collects reference data as well as the final transmission or reflectance measurement. This approach enables users to qualify instrument performance, anytime and without extra accessories. The wavelength region below 350 nm has very few, if any, standard reference materials (SRMs) (1). One reason is the energetic ultraviolet light materials must tolerate. There is also sensitivity of samples to contamination. Contamination by a monolayer of water, oxygen or oil has reportedly been responsible for transmission losses of 15% at 157 nm (2). The ability of the VUVAS to prove spectral and photometric precision in-situ provides valid data with confidence.

Figure 1 shows measured results and demonstrates precision. The VUVAS makes 0.05%T RSD measurements at 157 nm. Wavelength scanning over the 120 to 320 nm region results in data better than 0.3%T RSD. Overall instrument stability is better than 0.5%T per hour.

Figure 1

The VUVAS integrated system is a total solution. The one-touch vacuum (purge) control system and software allow users to perform high quality deep and vacuum ultraviolet measurements more easily and with higher confidence. It complements high performance UV-Vis instruments and provides solid performance for the deep and vacuum ultraviolet region.

Figure 2

References

(1) John P. Hammond C.Chem MRSC, New Certified Reference Materials for the determination of photometric accuracy in UV spectrophotometry, Spectroscopy Europe13(4) 2001.

(2) W. Pantely and D. Collier, "Taking the UV Challenge," OE Magazine, October 2001.

McPherson, Inc.

7A Stuart Road

Chelmsford, MA 01824

Tel. (800) 255-1055, (978) 256-4512

mcp@McPhersonInc.com

Website: www.McPhersonInc.com