sustainability analysis of metal assisted -...
TRANSCRIPT
SUSTAINABILITY ANALYSIS OF METAL ASSISTED
CHEMICAL ETCHING OF SILICON NANOWIRESFenfen Wang, Chris Yingchun YuanDepartment of Mechanical Engineering, UWM
Understand the sustainability performance of metal assisted chemical etching
(MACE) of silicon nanowires (SiNWs) for lithium ion batteries (LIBs).
Research Object: MACE of Si wafer for synthesizing SiNWs
•Quantify material consumptions and establish material flows of the process
•Analyze both airborne and waterborne emissions involved in the process.
Specifically, gas and gaseous particle emissions were tested using in-situ
measurements and particle emissions (including size distributions, concentrations,
morphologies, material compositions) in solutions were characterized by applying ex-
situ measurements.
•Provide first-hand data and information support for future scale-up of MACE
method for SiNWs and support the sustainable development of this technology.
➢ Etching parameters: 20 mM AgNO3 and 0.3 M H2O2.
OBJECTIVES EXPERIMENTAL CHARACTERIZATION EXPERIMENTAL CHARACTERIZATION (Cont.)
➢ Metal assisted chemical etching (MACE) of SiNWs has disadvantage of low
productivity with high material consumptions including large amount of toxic
chemicals. For example, for 1 g of SiNWs 39.6 g of Si wafer and 854.9 g of HF are
consumed, which are both economical and environmental concerns.
➢ Gas emissions including H2 and NO and large amount of gaseous particle emissions
are produced during the etching process. Most of the gaseous particles are with
diameters less than 100 nm. What is more, particle emissions are also found in the
etching solutions, which exert serious environmental and human health impacts.
➢ Further work is needed to study the possibility for improving the sustainability
performance of MACE of SiNWs by increasing its productivity and reducing
wastes.
CONCLUSION
• [1] Li, M., Li, Y., Liu, W., Yue, L., Li, R., Luo, Y., Trevor, M., Jiang, B., Bai, F., Fu, P.,
Metal-assisted chemical etching for designable monocrystalline silicon nanostructure.
Materials Research Bulletin, 76, 436-449, 2016.
BIBLIOGRAPHY
• Fenfen Wang, Email: [email protected]
• Chris Yingchun Yuan, Email: [email protected]
CONTACT INFORMATIONACKNOWLEDGEMENT
• This study is financially supported by the National Science Foundation (CBET-3560)
➢ Sustainability issues about MACE method
• Nano-particle emissions
• Large amount of material consumptions including toxic chemicals
Introduction
➢ Etching mechanism of MACE for SiNWs formation [1]:
➢ Experimental process of MACE for synthesizing SiNWs
Ag nucleation Ag nanoparticle
SiSi
Ag+
e
Si
SiO2
SiF62-
F-
Si
Ag+
e
e
Si
HF+AgNO3 HF+H2O2
Experimental flow chart for synthesis of SiNWs
Silicon
wafer
Acetone
Ethanol
DI-H2O
10 min
Cleaning
N2 blowing
Drying
HF+AgNO3
1 min
Etching
HF+H2O2
60 min
Etching
Diluted HF
2 min
Etching
HNO3
60 min
Cleaning
Removing Ag particles
Rinsing
&DryingSiNWs
DI-H2O
Synthesis process
Material inputs
➢ Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterizations
➢ Waterborne particle emissions
• Morphologies and element compositions of particles in solutions were
tested by SEM and energy-dispersive X-ray spectroscopy (EDS)
Material consumptions for synthesizing
1 g of SiNWs
Input Materials Mass (g)
Si Wafer (etched) 39.6
Acetone 495.2
Ethanol 494.6
DI-H2O 11055.6
HF (48%) 854.9
AgNO3 4.5
H2O2 (30%) 177.4
HNO3 (70%) 158.1
Output Mass (g)
SiNWs 1
Ag nanoparticles involved in SiNWs
Ag nanoparticles
600 nm
Nanoparticle size distributions in etching solution
300 400 500 600 700
0
20
40
60
80
100
Inte
nsity
Diameter (nm)
G (d)
C (d)
➢ Gas emissions
• Gas emissions including H2 and NO were tested using residual gas analyzer (RGA)
0 1000 2000 3000 4000
0.0
1.0x10-5
2.0x10-5
3.0x10-5
H2
NO
0.0
2.0x10-8
4.0x10-8
6.0x10-8
8.0x10-8
1.0x10-7
1.2x10-7
1.4x10-7
1.6x10-7
1.8x10-7
Time (s)
Pre
ssu
re (
To
rr)
➢ Gaseous particle emissions during the etching process
• Concentrations and size distributions of gaseous particle emissions were tested by ultrafine
Condensation Particle Counter (UCPC) and Scanning Mobility Particle Sizer (SMPS)
0 50 100 150 200 250
0
1x103
2x103
3x103
4x103
5x103
6x103
Co
nce
ntr
atio
ns (
#/c
m3)
Time (s)
From HF + AgNO3
(a)
0 1000 2000 3000 4000
0.0
2.0x104
4.0x104
6.0x104
8.0x104
1.0x105
Co
nce
ntr
atio
ns (
#/c
m3)
Time (s)
From HF + H2O2
(b)
0 1000 2000 3000 4000
0
1x105
2x105
3x105
4x105
5x105
6x105
Co
nce
ntr
atio
ns (
#/c
m3)
Time (s)
From HNO3
(c)
100 200 300 4000%
1%
2%
3%
4%
5%
20 40 60 80 1000%
1%
2%
3%
4%
5%
Perc
enta
ge
Diameter (nm)
Pe
rce
nta
ge
Diameter (nm)
From HF + AgNO3
(a)
0 100 200 300 400 500 600 7000%
1%
2%
3%
20 40 60 80 1000%
1%
2%
3%
Diameter (nm)
Pe
rce
nta
ge
Pe
rce
nta
ge
Diameter (nm)
(b)
From HF + H2O2
100 200 300 400 500 600 7000%
10%
20%
30%
40%
50%
100 200 300 400 5000%
1x10-3%
2x10-3%
3x10-3%
4x10-3%
Diameter (nm)
Pe
rce
nta
ge
Pe
rce
nta
ge
Diameter (nm)
(c)
From HNO3
In HF+H2O2 solution
In HNO3 solution
In HF+AgNO3 solution
O Ag
100 mAgOCBSE
C
7 mO FCBSE Si
F O Si
C
FAgO
100 mF OCBSE Ag
C