Supplementary Material
Oxidative Vaporization Etching for Molybdenum Tip Formation in Air
Yuto Goto1, Rie Suizu2, Yutaka Noguchi3, and Toyo Kazu Yamada1,3*
1. Department of Materials Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.
2. Department of Chemistry, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
3. School of Science and Technology, Meiji University, Kanagawa 214-8571, Japan.
4. Molecular Chirality Research Centre, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.

Author Information,Corresponding Author: Toyo Kazu Yamada *E-mail: toyoyamada@faculty.chiba-u.jp

Version 2020.11.20

1Flame etching setup.
Gasburner
flameMo wirebc5 mm

15 mm
x = 0 mmflame temp. [ K ]a. flame etchingflame
y15 mmy [ mm ]

y=0x

x=0

Centre of the flame

flame temp. [ K ]Lightflash!

into flame

d5 mm

y = 15 mm

micro torchx [ mm ]Figure S1. Flame etching of Mo wires. (a) Home-built flame etching setup. Upper and lower panels show
before and after the Mo wire insertion into the flame, respectively. (b) Gas burner flame spouted out fromthe micro torch. LP + O2 mixture gas was used. (c) Flame temperature along the y axis. (d) Flametemperature along the x axis.

2Flame-etching cycles at different flame positions.

SEM images (magnification ×30)
Tips

Total etching time (t)
1s
2s
3s
4s

5s

6s

7s

8s

9s

No.1
2300 Ky = 5 mm

No.2
No.3

2250 Ky = 10 mm

No.4

No.5
2100 Ky = 15 mm

No.6No.7

1950 Ky = 20 mm

No.8Figure S2. SEM images (magnification × 30) of the flame-etched Mo tips using different flame temperatureswith different numbers of flame-etching cycles.

3Flame-etching cycles at different flame positions.

SEM images (magnification ×10000)
Tips

Total etching time (t)
1s
2s
3s
4s

5s

6s

7s

8s

9s

No.1
2300 Ky = 5 mm

No.2
No.3

2250 Ky = 10 mm

No.4

No.5
2100 Ky = 15 mm

No.6
No.7

1950 Ky = 20 mm

No.8Figure S3. SEM images (magnification × 10000) of the flame-etched Mo tip apexes using different flametemperatures with different numbers of flame-etching cycles.

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X-ray diffraction Laue mapping of the flame-etched Mo tips

X-ray Laue images (camera length 40mm)a

Ball region

Rod regionbω scanc Apex region

Ball region

Rod region

Figure S4. X-ray diffraction Laue images obtained from the flame-etched Mo tip apexes: (a) ball and (b)rod regions. (c) ω scan Laue mappings obtained at apex, ball, and rod regions.

5Crystalline structures and space groups of Mo and Mo-oxides.

Bravaisspace groupa (Å)
b (Å)
c (Å)
 (°)
 (°)
 (°)
V (Å3)Mo1)Cubic
Im-3m
3.144
----909090
31.08

MoIVO22)
Monoclinic
P21/c
5.54054.85735.626590119.68990
131.542

MoVIO3 a3)
Orthorhombic
Pnma
14.02
3.70283.96639090
90205.904

MoVIO3 b4)
Monoclinic
P21/c
7.12285.366
5.5665
90
92.01
90
212.626

MoVIO3 c5)
Monoclinic
P21/c
7.415
7.433
10.648490134.04590
421.856

MoVIO3 d6)
Monoclinic
P21/m
3.954
3.687
7.095
90
103.7590
100.47

Figure S5. Crystalline structures and space groups of Mo and Mo-oxides.

References
1) J. Am. Ceram. Soc., 75, 1412 (1992)
2) Aust. J. Chem., 48, 1473 (1995)
3) J. Appl. Crystallogr., 21, 960 (1988)
4) J. Solid State Chem., 93, 193 (1991)
5) Mater. Sci. Forum, 27/28, 85 (1988)
6) J. Solid State Chem., 91, 121 (1991)

Video 1This movie (mp4 file, 4 seconds, 10 MB) shows the flame etching process of a Mo wire.
The file name: Video1_MoTip_flame_etching.mp4

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