Supporting Information
Transmission Type Flat-Panel X-ray Source Using ZnO Nanowire Field
Emitters
Daokun Chen1,2, Xiaomeng Song1,2, Zhipeng Zhang1,2, Ziping Li3, Juncong
She1,4, Shaozhi Deng1,4, Ningsheng Xu1,4 and Jun Chen1,2,a)
1State
Key Laboratory of Optoelectronic Materials and Technologies, Guangdong Province Key Laboratory
of Display Material and Technology, Sun Yat-sen University, Guangzhou 510275, China
2School
3The
of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275, China
First Affiliated Hospital, Sun Yat-sen University, Guangzhou 510275, China
4School
of Microelectronics, Sun Yat-sen University, Guangzhou 510275, China
_____________________________
a)
Author to whom correspondence should be addressed. Electronic mail: stscjun@mail.sysu.edu.cn.
S1
S1. The result of resistance of individual ZnO nanowire
Figure S1(a) shows the schematic of experimental setup for resistance measurement of
individual ZnO nanowire. The measurement was carried out in an Omicron Nanoprobe system,
which equipped with SEM and nanoprobes driven by piezo motors. The I-V characteristics of
individual ZnO nanowire were measured by contacting the tungsten probe with the apex of the
nanowire. A typical I-V characteristic curve is presented in Fig. S1(b). The resistance can be
calculated from the linear part of the I-V curve at high applied voltage, and the resistance value
of 695 MΩ is estimated for this single ZnO nanowire. We measured several dozen ZnO
nanowires and the obtained resistances are in the range of 100-800 MΩ, which is consistent with
our previous report.1
FIG. S1. (a) The schematic diagram of experimental setup for the resistance measurement of
individual ZnO nanowire. (b) A typical I-V characteristic curve of a single ZnO nanowire. The
inset is the SEM image showing the W probe in contact with the tip of ZnO nanowire for
resistance measurement.
S2
S2. The calculation of X-ray divergence angle in our flat-panel X-ray source
Figure S2 shows the schematic drawings of the generation of X-rays with a divergence
angle θ ( 0 ≤ θ ≤ 90° ) and the imaging geometry for a metal mesh by our flat-panel X-ray
source. In order to obtain a resolved X-ray image, some relationships of geometrical parameters
shown in Figs. S2(b) need to meet the requirements that can be described as
2(𝑏 + ℎ) ∙ 𝑡𝑎𝑛𝜃 + 𝑎 = 𝑎′
(S2.1)
2(𝑏 + ℎ) ∙ 𝑡𝑎𝑛𝜃 + 𝑑 ′ = 𝑑
(S2.2)
d′ > 0
(S2.3)
Here a, b, d are the line width, thickness, and aperture of the metal mesh, respectively. h is
the gap between mesh and imaging sensor. 𝑎′ and 𝑑′ are corresponding line width and aperture
acquired from the X-ray image of the metal mesh. In our study, a very clear X-ray image was
obtained, as shown in Fig. 4(a). In this situation, a=0.20 mm, 𝑎′ =0.35 mm, b=0.10 mm, d=0.45
mm, 𝑑′=0.30 mm, and h is estimated to be 1.0 mm including the thickness of the encapsulation
of the sensor. As a result, the divergence angle θ is calculated to be about 3.9°.
FIG. S2. (a) The emitted X-rays with a divergence angle θ from our flat-panel X-ray source. (b)
Imaging geometry for a metal mesh in our case.
S3
Reference for supporting information
1
C. X. Zhao, K. Huang, S. Z. Deng, N. S. Xu, and J. Chen, Appl. Surf. Sci. 270, 82 (2013).
S4