NASA Technical Reports Server (NTRS) 20100014082: Selective Plasma Deposition of Fluorocarbon Films on SAMs

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by  NASA Technical Reports Server (NTRS)

Materials
Ion-Exclusion Chromatography for Analyzing Organics in Water
Resolution of nonvolatile organic compounds is increased significantly.
Lyndon B. Johnson Space Center, Houston, Texas
A liquid-chromatography technique
has been developed for use in the quan- PRIOR TECHNIQUE PRESENT (IMPROVED) TECHNIQUE
titative analysis of urea (and of other 1.2 20.0
?
nonvolatile organic compounds typically Unknown Impurities
found with urea) dissolved in water. The 1.0 17.5
technique involves the use of a column
that contains an ion-exclusion resin; Urea, 15 Parts per Million 15.0
heretofore, this column has been sold 0.8 1.5 mL/minute Water, 0.5 mL/minute Water,
for use in analyzing monosaccharides mAU 21205-n-Lm S Daemtepcleti,on mAU12.5 19265-n-Lm S Daemtepcleti,on
awtbcohnea Tredtaoenh fnrm oe as ooalupytndpozr eepsig oo rlrioafwe tpfeast he.ntehcyerh ir g(nshfH,io q-bpPruu eLeturC nfroc)eoo,ra tmm wfcoamiotnrh noca ntenre leanylll tiiyaqu znushineciaddges Chromatographic Intensity, 000...246 Chromatographic Intensity, 1075...050 ?? = Unknown Impurity Urea, 4 Parts
on hydrophobic interactions between an- per Million
alytes in a water sample and long-chain ? ? ? ? ?
alkyl groups bonded to an HPLC col- 0.0 2.5
umn. The prior technique has proven in- ? ?
adequate because of a strong tendency –0.2 0
toward co-elution of urea with other com- 0 1 2 3 4 5 0 5 10 15 20 25 30 35 40
pounds. Co-elution often causes the urea Time, M inutes Time, M inutes
and other compounds to be crowded into
These Chromatogramswere made from samples of space-shuttle humidity condensate, which con-
a narrow region of the chromatogram tained dissolved urea and other impurities.
(see left part of figure), thereby giving
rise to low chromatographic resolution charge. As a result, the degree of separa- measured is reduced (to between 1/5
and misidentification of compounds. It is tion is increased: instead of being and 1/3 of that of the prior technique)
M SC23000
possible to quantitate urea or another an- crowded together into a single chro- because it is not necessary to dilute the
6-23-00 bs
alyte via ultraviolet- and visible-light ab- matographic peak only about 1 to 2 min- sample.
sorbance measurements, but in order to utes wide as in the prior technique, the • The separation of peaks facilitates the
perform such measurements, it is neces- chromatographic peaks of different identification and quantitation of the
sary to dilute the sample, causing a signif- compounds are now separated from various compounds. The resolution of
icant loss of sensitivity. each other and spread out over a range the compounds other than urea makes
The ion-exclusion resin used in the about 33 minutes wide (see right part of it possible to identify those com-
improved technique is sulfonated poly- figure), and the urea peak can readily be pounds by use of mass spectrometry.
styrene in the calcium form. Whereas distinguished from the other peaks. This work was done by Richard Sauer of
the alkyl-chain column used in the prior Although the analysis takes more time Johnson Space Center and Jeffrey A.
technique separates compounds on the in the improved technique, this disad- Rutz and John R. Schultz of Wyle Laborato-
basis of polarity only, the ion-exclusion- vantage is offset by two important ad- ries. For further information, contact the
resin column used in the improved tech- vantages: Johnson Commercial Technology Office at
nique separates compounds on the basis • Sensitivity is increased. The minimum [phone].
of both molecular size and electric concentration of urea that can be MSC-23000
Selective Plasma Deposition of Fluorocarbon Films on SAMs
The fluorocarbon films are useful as etch masks and perhaps as dielectric layers.
Goddard Space Flight Center, Greenbelt, Maryland
A dry plasma process has been These SAMs are used, during the fabri- porated into the devices. The selective
demonstrated to be useful for the selec- cation of semiconductor electronic de- modification involves the formation of
tive modification of self-assembled vices, as etch masks on gold layers that fluorocarbon films that render the SAMs
monolayers (SAMs) of alkanethiolates. are destined to be patterned and incor- more effective in protecting the masked
NASA Tech Briefs, January 2006 13
an alkanethiolate SAM in the desired
pattern (see figure). Next, the work-
piece is exposed to a radio-frequency
plasma generated from a mixture of CF
4
and H gases. After this plasma treat-
2
ment, the SAM is found to be modified,
while the exposed areas of gold remain
unchanged.
This dry plasma process offers the po-
tential for forming masks superior to
those formed in a prior wet etching
SAM Mask After Modification Gold Remaining in Masked Areas process. Among the advantages over the
After Etching in KI Solution wet etching process are greater selectiv-
ity, fewer pin holes in the masks, and less
A Gold Layer Was Patternedby stamping it with a hexadecanethiol solution. The alkanethiolate SAM
pattern thus formed was modified in a CF/H plasma, forming an etch mask. Then gold was etched nonuniformity of the masks. The fluoro-
4 2
away from the areas not masked. carbon films formed in this way may also
GSC-14440 be useful as intermediate layers for sub-
ABPI
areas of the gold against etching by a sired pattern is fabricate0d5- 2b5y-0 4s tandaLrEd sequent fabrication steps and as dielec-
potassium iodide (KI) solution. This photolithographic techniques. A stamp tric layers to be incorporated into fin-
modification can be utilized, not only in is then made by casting polydimethyl- ished products.
the fabrication of single electronic de- siloxane (commonly known as silicone This work was done by Mark M. Crain III,
vices but also in the fabrication of inte- rubber) in the mold. The stamp is Kevin M. Walsh, and Robert W. Cohn of the
grated circuits, microelectromechanical coated with an alkanethiol solution, University of Louisville for Goddard Space
systems, and circuit boards. then the stamp is pressed on the gold Flight Center. Further information is con-
In the steps that precede the dry layer of a device to be fabricated in tained in a TSP (see page 1).
plasma process, a silicon mold in the de- order to deposit the alkanethiol to form GSC-14440
Water-Based Pressure-Sensitive Paints
Toxicity, and thus costs of ventilation and cleanup, is substantially reduced.
Langley Research Center, Hampton, Virginia
Water-based pressure-sensitive paints the light emitted from the luminescent PSP is inversely proportional to the con-
(PSPs) have been invented as alterna- compound; and centration of oxygen, hence, to the air
tives to conventional organic-solvent- • Solvents. pressure at the painted surface.
based pressure-sensitive paints, which The paint is applied to a surface of in- A water-based PSP contains all the
are used primarily for indicating distri- terest on a model and allowed to dry. basic ingredients of a conventional PSP
butions of air pressure on wind-tunnel During a subsequent wind-tunnel test, (see table), except that the organic-sol-
models. Typically, PSPs are sprayed onto under the appropriate illumination, the vent content (if any) is much smaller
aerodynamic models after they have intensity of luminescence emitted by the and the basic ingredients are incorpo-
been mounted in wind tunnels. When
conventional organic-solvent-based PSPs
Proportion in
are used, this practice creates a problem Ingredient Weight Percent
of removing toxic fumes from inside the
wind tunnels. The use of water-based water emulsion of
poly-trifluoroethylmethacrylate-co-isobutylmethacrylate (1:1) 42 to 68.4
PSPs eliminates this problem. The water-
based PSPs offer high performance as propylene glycol 2.28
pressure indicators, plus all the advan-
a glycol ether 10.26
tages of common water-based paints
(low toxicity, low concentrations of TiO (pigment) 11.35
2
volatile organic compounds, and easy
cleanup by use of water). N-methyl pyrrolidinone 6.00
A typical PSP (whether conventional
Byk 346
or of the present innovative type) con- (or equivalent solution of polyether-modified dimethylpolysiloxane) 0.68
tains the following:
• A luminescent compound, the lumines- Lubrizol 2062 (or equivalent) aliphatic/aromatic phosphate ester
for solvent-borne and water-borne coatings 1.03
cence of which is quenched by oxygen;
• An oxygen-permeable polymeric platinum tetra(pentafluorphenyl)porphyrin (a luminophore) 0.1
binder;
• Pigment materials to hide the painted
surface and to increase reflectance of A Typical Water-Based PSP Formulationis shown here.
14 NASA Tech Briefs, January 2006