Supporting Information for

Autonomy in materials research: A case study in carbon nanotube growth

Pavel Nikolaev1,2, Daylond Hooper1,2,*, Frederick Webber1,2,**, Rahul Rao1,2, Kevin Decker1,2, Michael Krein3, Jason Poleski3, Rick Barto3, and Benji Maruyama1.

1. Air Force Research Laboratory, Materials and Manufacturing Directorate, RXAS, WPAFB, OH 45433, USA.

2. UES Inc., Dayton, OH 45432, USA.

3. Lockheed Martin Advanced Technology Laboratories, Cherry Hill, NJ 08002, USA

* Present affiliation: Air Force Research Laboratory, RHCI, WPAFB, OH 45433 and Infoscitex Inc., Dayton, OH 45431, USA.

** Present affiliation: Air Force Research Laboratory, 711 Human Performance Wing, Human Effectiveness Directorate, RHAS, WPAFB, OH, 45433, USA


Figure S1. ARES instrument diagram. 1. Laser. 2. Beam splitter. 3. Objective lens. 4. Quartz window. 5. Growth chamber. 6. Sample wafer holder. 7. Gas in from mass flow controllers and water source (not shown). 8. Gas out to vacuum pump (not shown). 9. x-y motion stage. 10. Notch filter. 11. Lens. Inset shows SEM image of the pillars.


Figure S2. Results of a typical experiment. a, Appearance and increase in intensity of G- and D-bands during CNT nucleation and growth in 5 s time increments. Peaks are broadened and blue-shifted due to ~900oC temperature. b, The corresponding growth curve: G-band area plotted vs. time. Fit to the Equation 2, is shown in red. Maximum growth rate is obtained at the inflection point . c, The resulting Raman spectrum at room temperature is characteristic of high quality single-wall nanotubes: G-band is split into G+ and G- components, and D/G band ratio is ~0.03.

Figure S3. Slices through 4-dimentional parameter space. a, Growth rate in the vicinity of 940 oC temperature and 8 Torr hydrogen partial pressure (parameters that were found to maximize the growth rate in Task 10). Growth rate has a maximum when water/ethylene ratio is close to 1.6 x 10-3. b, Arrhenius plot of the growth rate in the vicinity of 8 Torr hydrogen partial pressure, 12 Torr ethylene partial pressure and 1.6 x 10-3 water/ethylene ratio. Arrhenius fit results in 1.1 ± 0.3 eV activation energy.

Table S1. Objective growth rates and number of experiments in each task.

Task Number / Objective growth rate / Number of experiments
1* / 100 – 10,000 / 93
2 / 900 / 29
3 / 500 / 94
4 / 10,000 / 57
5 / 3000 – 5000 / 47
6 / 4000 / 81
7 / 9000 / 62
8 / 8000 / 72
9** / 16,000 / 37
10 / 16,000 / 61

*The goal was to initially sample as much of the parameter space as possible.

**Planner was challenged, with all predicted rates less than 12,000.

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