Arnold, J. O.

Meyyappan, M.

NASA Technical Reports Server

National Aeronautics and 
Space Administration
Entry Systems and Technology Division
Ames Research Center
Silicon Carbide, Vacuum Tube Nanoelectronics:  
Application for Exploration Missions Requiring 
Category III/IV Planetary Protection
J. O. Arnold1 and Meyya Meyyappan2
1AMA at NASA Ames Research, Moffett Field CA, 94035
2NASA Ames Research Center, Moffett Field CA, 94035
Acknowledgment:  Jin-Woo Han 
IPPW 15, June 13, 2018, Boulder CO
https://ntrs.nasa.gov/search.jsp?R=20180006872 2019-08-31T17:59:44+00:00Z
Outline
• Category III/IV Planetary Protection Policy - Purpose and applicable 
missions. [1] Space Research Today, COSPAR Bulletin # 200 Dec. 2017.
• Penetrating  sterilization techniques and incompatibilities (Pugel, et. 
al., March  2017 IEEE Aerospace Conference) [2].
• Why and what are SiC vacuum tube nanoscale electronic systems  that 
are being funded for development by NASA SMD? [3]. What attributes 
make them amenable to penetrating  sterilization by simultaneous 
application of  dry heat and irradiation? 
• Take home message 
• Forward work 
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Category III/IV Planetary Protection [1]
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• Committee on Space Research (COSPAR) maintains international 
standards and procedures  to guide compliance with a UN Space     
Treaty to avoid biological contamination of bodies resulting from     
Space Exploration. 
• Category III (mostly flyby and orbital) and IV(mostly probes and 
landers)  apply to forward contamination of  Enceladus, Europa,      
Mars “Special Regions”  and others “TBD”.  
• For Enceladus and  Europa, the probability of inadvertent 
contamination of their oceans by terrestrial organisms is to be             
less than 1X10-4 per mission. 
• Mars  requirements are subdivided into four  categories:  One for 
orbiters and  three for landers at “special regions” depending upon 
mission objectives relating to the search for extant Martian Life.          
See [1] for detail.
Policy compliance requires spacecraft sterilization and      
any recontamination. Ideally, dead spores are removed. 
From “Brushing your spacecraft’s teeth ”A review of
Penetrating Bio Reduction Processes”  March 2017 [2]
Technique Examples of Potential Incompatibilities
Dry Heat Microbial 
Reduction (DHMR)
Thin films, Joints or interfaces with disparate 
coefficients of thermal expansion.
Gamma Rays
(Cobalt 60)
Radiation sensitive electronics.  Polymer 
degradation.
Gamma Rays 
Plus Heat
Electronics rated for less than 100-150 krad
and 95-100 OC.
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• “Dry Heat Microbial Reduction (DHMR): NASA and ESA have  approved DHMR 
processes.   “NASA has invested in qualification of DHMR hardware.” 
• ”Gamma Scalability is already a reality.  DoD and the Dept. of Homeland Defense
use Gamma Radiation for  Sterilization.” 
• “Dead microbes are not removed by the gamma process, so additional methods would be      
required if organic  contamination is a requirement for planetary protection.” 
•  “Gamma + Heat (Thermoradiation): Promising for parts, subsystems, or integrated 
systems that  may be able to tolerate test parameters for temperature and  radiation.”
SiC Vac Tube Nanoscale  Electronics [3]
Presently tested at 200 OC &1 Mrad
Vacuum ambient
<50nm
<5nm
Back gate
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• Manufactured with standard  Integrated Circuit  plasma etching techniques. 
• SiC -> Temps from  500 to 600 OC; Vac. Tube  Technology -> Rad. Resistance 
> 1 Mrad -> High likelihood for Penetrating Sterilization via Thermoradiation.
• Temps to 500 – 600  OC  -> Dead spore removal via dry heat ashing [4]? 
Cobalt 60 Gamma Rays + Heat = THERMORADIATION
Resear
ch
Spacecraft
Electronics
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Sterilization Approach
Synergy of Thermoradiation [2]  
N(t) = Noe-( kT + kR + kTR)t    [5]
• 2.5 Mrad alone to kill 
“standard” spores.
• 95 – 110 OC + 150 Krad
gives 4 – 7 logs spore 
reduction in 15 hours.
How would sterilization affect 
SiC nanoelectronics performance? 
Take Home Message
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• SiC Vacuum tube nanoscale electronics is an emerging technology 
funded by SMD for future missions to Europa because of its    
resistance to high levels of radiation. 
• Attributes of the emerging technology strongly suggest it is amenable 
to: (1)  sterilization by thermoradiation and (2) removal of  dead  
spores and organic residue by ashing to 600 OC.
If this proves to be the case, the potential incompatibility in use  
of thermoradiation for electronics sterilization for category III/IV 
missions to Enceladus, Europa  and Mars   “Special Regions” 
could be overcome. 
Forward Work
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•  Fabricate and demonstrate SiC Vacuum tube nanoscale
electronic circuits that can operate at 500 OC under 1 Mrad
radiation within 2 years (Funded by SMD).
Additionally, the value of the technology could be greatly enhanced by:
•  Demonstrating   Microbial reduction via Thermoradiation as
described in  NASA SP-5105 [5] and the rate equation shown above. 
•  Evaluate removal of dead spores and organic residue by ashing
to temperatures approaching 600 OC.
•  Demonstrate performance of nanoscale electronics pre/post
sterilization and ashing.  
If this research was conducted and positive outcomes
realized, it is possible that sterilizable, spore free, SiC
nanoscale electronics could be available for future missions 
to Enceladus, Europa and “Special Regions” on  Mars.
References
[1] “Space Research Today, COSPAR’s Information Bulletin”, No. 200, pp
11-25, December 2017.
[2] Pugel, D. E., Rummel, J. D., and C. Conley, “Brushing Your Spacecraft’s Teeth: A 
Review of Biological Reduction Processes for Planetary Protection Missions”,  IEEE 
Aerospace Conference March 2017. 
[3] Han, J.W., Moon, D.I., and Meyyappan, M. “ Nanoscale Vacuum Channel Transistor, 
Nano Letters, 17, 2146-2151 (2017). 
[4] Barnes, R. M., et.al., “Introduction for Preparation  for Trace Element 
Determination”.  In Microwave Assisted Sample Preparation for Trace Element Analysis, 
2014, https://www.sciencedirect.com/science/book/9780444594204
[5] NASA SP-5105, “Advances in Sterilization and Decontamination, A Survey” 1978.
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National Aeronautics and 
Space Administration
Entry Systems and Technology Division
Ames Research Center
Questions?
James.O.Arnold@NASA.gov
M.Meyyappan@NASA.gov
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Backup
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1970’s Viking PP Approach
Photo Shows the entire 
1976 Viking Lander 
being prepared for final  
sterilization:  Heated to 
120 OC for 30 hours. It’s 
still the “Gold Standard” 
of Planetary Protection
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Silicon Carbide, Vacuum Tube Nanoelectronics: Application for Exploration Missions Requiring Category III/IV Planetary Protection

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