Supplementary Information:
Current-modulated optical properties of vanadium dioxide thin films in the
phase transition region
Shuyan Zhang, Mikhail A. Kats, Yanjie Cui, You Zhou, Yu Yao, Shriram Ramanathan,
and Federico Capasso*
School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
*capasso@seas.harvard.edu
Here we present additional information on the characterization of the device including
electrical and optical measurements as a function of temperature.
Fig. S1(a) shows the resistance change as a function of temperature in a log scale
measured by a home-made 2-probe station with a calibrated temperature stage. Resistance values
were taken at every 2 degrees Celsius. The resistance on/off ratio is 𝑅25 𝑜𝐶 ⁄𝑅100 𝑜𝐶 = 610. To
determine the transition temperature TIMT and the hysteresis, we plot the 𝑑[𝑙𝑜𝑔(𝑅)]⁄𝑑𝑇 in Fig.
ℎ𝑒𝑎𝑡𝑖𝑛𝑔
S1(b). The maxima occur at 𝑇𝐼𝑀𝑇
𝑐𝑜𝑜𝑙𝑖𝑛𝑔
= 71 𝑜𝐶 and 𝑇𝐼𝑀𝑇
= 67 𝑜𝐶 . Hence the hysteresis width
is the difference between the two which is 4 oC.
5
10
0.3
Increasing Temp.
Decreasing Temp.
0.2
4
d(log(R))/dT
Resistance ()
Increasing Temp.
Decreasing Temp.
10
3
10
0.1
0
-0.1
2
10
20
40
60
80
-0.2
20
100
o
40
60
80
100
o
Temperature ( C)
Temperature ( C)
(a)
(b)
Fig. S1. (a) Study of resistance change above and below the phase transition. (b) Determination of the
transition temperature and the hysteresis width during heating and cooling.
1
Fig. S2(a) and (b) show the reflectance spectra at different temperatures for the heating
and cooling cycles respectively. The measurements were performed with Bruker Fourier
transform infrared (FTIR) spectrometer with a Hyperion 3000 FTIR microscope. Above the TIMT,
VO2 is in its metallic phase which has a high reflectance close to 0.6 whereas below the TIMT,
VO2 is insulating which has a low reflectance of about 0.2 and it decreases as the wavelength
increases. This observation is consistent with Fig. 4(d) in the main article. The close-to-zero
reflectance point at about 11.6 µm is a result of critical coupling and is used as the perfect
absorber condition discussed in Ref. 1. Unfortunately our Focal Plane Array detector has a
limited spectral range, so this feature is not captured in Fig. 4 in the main article.
1
0.6
0.4
0.6
0.4
0.2
0.2
0
90 C
70 C
68 C
67 C
60 C
50 C
23.8 C
0.8
Reflectance
0.8
Reflectance
1
21.6 C
40 C
65 C
70 C
71 C
72 C
80 C
100 C
5
10
0
15
5
10
15
Wavelength(m)
Wavelength(m)
(a)
(b)
Fig. S2. Reflectance spectra at different temperatures during the heating cycle (a) and the cooling cycle
(b).
Reference:
1
M. A. Kats, D. Sharma, J. Lin, P. Genevet, R. Blanchard, Z. Yang, M. M. Qazilbash, D. N. Basov,
S. Ramanathan, and F. Capasso, Applied Physics Letters 101 (22) (2012).
2