CN103674880A - TM (transverse magnetic) polarization graphene nanobelt array sensor - Google Patents

Abstract

The invention discloses a TM (transverse magnetic) polarization graphene nanobelt array sensor for an infrared band. The period and the duty ratio of a graphene nanobelt array on the top of the sensor are respectively 245-255 nanometers and 0.45-0.55; the fermi level is 0.65-0.75eV. When TM polarization light of the infrared band is incident perpendicularly, the sensitivity of the TM polarization light to gas (the refractive index change range is 1.0-1.05) is higher than 2,520nm/RIU, and the quality factor is larger than 6.25; the sensitivity of the TM polarization light to a low-refractive-index material (the refractive index change range is 1.30-1.35) in a water environment is higher than 2,920nm/RIU, and the quality factor is larger than 6.27. Due to different Fermi levels, the sensor can be synchronously used for detecting the gas and the low-refractive-index material in the water environment. The sensor disclosed by the invention is obtained by combining an electronic beam direct-write device with a micro-electronic deep etching technology; the materials are readily available; the manufacturing cost is low; large-batch production can be realized; the sensor has an important practical prospect.

Description

TM polarization graphene nanobelt sensor array

Technical field

This patent relates to graphene nanobelt sensor array, particularly a kind of TM polarization graphene nanobelt sensor array for infrared band.

Background technology

Traditional surface plasma resonance sensor, based on metal-dielectric structure, is mainly used in visible and near-infrared band.However, for mid and far infrared frequency, surface plasma wave is no longer attached to metal-dielectric interface, and this is restricted the sensitivity of sensor.For this reason, people have proposed the graphene nanobelt sensor array of middle-infrared band.Its ultimate principle is, in probing medium, the slight variation of refractive index, will cause surface plasma wave vector to change, and this can move to obtain by measuring the spectrum of resonance transmission peaks.Graphene-based nanostructured can be supported height-limited plasma mode, because the conductivity of Graphene can be carried out dynamic adjustments by chemistry or static switching form, make Graphene plasma mode to realize dynamic regulation at infrared-terahertz wave band.These characteristics can carry out graphene nanobelt sensor array tuning within the scope of very wide wavestrip, and therefore, it is with a wide range of applications as novel senser element.

The people such as B.Vasic have inquired into the possibility of utilizing graphene nanobelt array to survey variations in refractive index in dielectric environment first theoretically, and utilize Graphene surface plasma to survey pure dielectric and the diffusion film of mode of oscillation.However, the outer coupling efficiency of designed device, namely reflection efficiency very little (<0.16) [formerly technology 1:B.Vasic et al., J.Appl.Phys., 113,013110 (2013)].The people such as Y.Zhao have proposed the transmission-type biology sensor of infrared band, and studied the specific inductive capacity of substrate in great detail, Fermi level and structural parameters are on the impact of transducer sensitivity and precision [technology 2:Y.Zhao et al. formerly, Phys.Chem.Chem.Phys., 15,17118 (2013)].However, current the proposed sensor based on graphene nanobelt array, is mainly used in surveying single ranges of indices of refraction.

Graphene nanobelt sensor array is the Graphene grating of rectangular channel in essence.Rectangular raster is to utilize micro-nano processing technology, the grating with rectangle flute profile processing on substrate.The Diffraction Problems of subwavelength grating with rectangular grooves, can not be processed by simple scalar optical grating diffraction, and must adopt the Maxwell equation of vector form and in conjunction with boundary condition, by the computer program of encoding, accurately solve.The people such as Moharam have provided the algorithm [formerly technology 3:M.G.Moharam et al., J.Opt.Soc.Am.A.12,1077 (1995)] of rigorous coupled wave theory, can solve the Diffraction Problems of this class sub-wave length grating.As far as we know, up to the present, also nobody for infrared band be given on fused quartz substrate, make based on graphene nanobelt array structure, can be simultaneously for surveying the sensor of the low-index material of hydrogen and water environment.

Summary of the invention

The technical problem to be solved in the present invention is to provide a kind of TM polarization graphene nanobelt sensor array for infrared band.When the TM of infrared band polarized light vertical incidence, it is the 2520nm that is changed to that per unit variations in refractive index causes resonance wavelength to the highly sensitive of gas (variations in refractive index scope is 1.0-1.05) in 2520nm/RIU(), quality factor is greater than 6.25, it is highly sensitive in 2920nm/RIU to the low-index material in water environment (variations in refractive index scope is 1.30-1.35), and quality factor is greater than 6.27.By adopting different Fermi levels, this sensor can be simultaneously for the low-index material of probe gas and water environment.Therefore, this sensor has important practical value.

Technical solution of the present invention is as follows:

For a TM polarization graphene nanobelt sensor array for infrared band, the cycle that it is characterized in that the top graphene nanobelt array of this sensor is that 245～255 nanometers and dutycycle are 0.45～0.55, and Fermi level is 0.65～0.75eV.

Cycle and the dutycycle of the top graphene nanobelt array of best sensor are respectively 250 nanometers and 0.5, and Fermi level is 0.7eV.

Technique effect of the present invention is as follows:

Cycle and the dutycycle of particularly working as the top graphene nanobelt array of sensor are respectively 250 nanometers and 0.5, when Fermi level is 0.7eV, when the TM of infrared band polarized light impinges perpendicularly on this device, TM polarization graphene nanobelt sensor array is 2840nm/RIU to the sensitivity of gas (variations in refractive index scope is 1.0-1.05), quality factor is 7.17, it is 3280nm/RIU to the sensitivity of the low-index material in water environment, and quality factor is 7.06.

That the present invention has is flexible and convenient to use, refractive index is highly sensitive, and quality factor advantages of higher, is a kind of desirable senser element.

Utilize electron-beam direct writing device in conjunction with Microelectronic etching technique, the present invention can be in enormous quantities, produce at low cost, and the sensor performance after making is stable, reliable, has important practical prospect.

Accompanying drawing explanation

Fig. 1 is the geometry schematic diagram of the TM polarization graphene nanobelt sensor array for infrared band of the present invention.

In figure, 1 represents that (refractive index is n in probing medium region ₁), 2 represent grating, and grating layer material is Graphene (Graphene), and 3 represent that (refractive index is n to substrate _s), 4 represent the incident of TM polarized light.D is the cycle of graphene nanobelt array, the width that w is graphene nanobelt, and f=w/d is the dutycycle of graphene nanobelt array, the thickness that h is graphene layer.

Fig. 2 is an embodiment in claimed range of the present invention, and when the refractive index of probing medium changes between 1.0～1.05, the zero level efficiency of transmission of TM polarized light is with the curve of wavelength variations.

Fig. 3 is embodiment in Fig. 2, and when the refractive index of probing medium changes between 1.30～1.35, the zero level efficiency of transmission of TM polarized light is with the curve of wavelength variations.

Embodiment

Below in conjunction with embodiment and accompanying drawing, the invention will be further described, but should not limit the scope of the invention with this.

First refer to Fig. 1, Fig. 1 is that the present invention is for the geometry schematic diagram of the TM polarization graphene nanobelt sensor array of infrared band.In figure, region 1,2 is all uniformly, is respectively probing medium and fused quartz (refractive index n _s=1.45),, when probing medium is gas, corresponding variations in refractive index scope is n ₁=1.0～1.05, when probing medium is the low-index material in water environment, corresponding variations in refractive index scope is n ₁=1.30～1.35, TM polarized light (corresponding to the direction of vibration of magnetic vector perpendicular to the plane of incidence) impinges perpendicularly on this device.As seen from the figure, the present invention is for the TM polarization graphene nanobelt sensor array of infrared band, and cycle and the dutycycle of the top graphene nanobelt array of this sensor are respectively 245～255 nanometers and 0.45～0.55, and Fermi level is 0.65～0.75eV.

Under geometry as shown in Figure 1, the present invention adopts rigorous coupled wave theoretical [formerly technology 3] to calculate the zero level efficiency of transmission of this TM polarization graphene nanobelt sensor array within the scope of infrared band.We utilize rigorous coupled wave theoretical [formerly technology 3] and simulated annealing rule [technology 4:W.Goffe et al. formerly, J.Econometrics60,65-99 (1994)] be optimized, thus obtain the TM polarization graphene nanobelt sensor array of this high sensitivity and high-quality-factor.

Table 1 has provided a series of embodiment of the present invention, and in table, d is the cycle of graphene nanobelt array, the width that w is graphene nanobelt, and f=w/d is the dutycycle of graphene nanobelt array, the thickness that h is graphene layer.S _{λ 1}represent transducer sensitivity when refractive index when probing medium is 1.0～1.05 variations, FOM ₁for corresponding quality factor.S _{λ 2}represent transducer sensitivity when refractive index when probing medium is 1.30～1.35 variations, FOM ₂for corresponding quality factor.

Graphene can be regarded a kind of anisotropic material as, when room temperature T=300K, for mid and far infrared frequency wherein

for reduced Planck constant, ω is angular frequency, E _ffor Fermi level, the optics conductivity of Graphene can be similar to a Drude model:

Wherein, e is elementary charge, and τ is carrier relaxation time.When emulation, Graphene can be modeled to the thin layer of a layer thickness h=0.34nm, in its face, specific inductive capacity is:

${\mathrm{\&epsiv;}}_g=1+\frac{\mathrm{i\&sigma;}\left(\mathrm{\&omega;}\right)}{{\mathrm{\&epsiv;}}_0\mathrm{\&omega;h}}---\left(2\right)$

From (1) formula and (2) formula, can find out, change Fermi level, can change the conductivity of Graphene, thereby can adjust the specific inductive capacity of Graphene.

While meeting surface plasma resonant vibration condition, as the variations in refractive index δ of probing medium n ₁time, resonance wavelength moves δ λ _sPP, the refractive index sensitivity definition of the sensor based on graphene nanobelt array is δ λ _sPPwith δ n ₁ratio:

$S_{\mathrm{\&lambda;}}=\frac{{\mathrm{\&delta;\&lambda;}}_{\mathrm{SPP}}}{{\mathrm{\&delta;n}}_1}---\left(3\right)$

S _λunit be nm/RIU.Because designed sensor is transmission-type structure, in order to compare the overall performance of sensor, quality factor (FOM) is defined as:

$\mathrm{FOM}=\frac{S_{\mathrm{\&lambda;}}}{\mathrm{FWHM}}\mathrm{\&Delta;T}---\left(4\right)$

Wherein, the full width at half maximum that FWHM is transmitted spectrum, Δ T=1-T _min, T _minfor the minimum value of efficiency of transmission, the efficiency of transmission of resonance wave strong point namely.

When making the present invention is used for the TM polarization graphene nanobelt sensor array of infrared band, suitably select cycle and dutycycle and the Fermi level of top graphene nanobelt array, just can obtain the TM polarization graphene nanobelt sensor array of high sensitivity and high-quality-factor.

Fig. 2 is an embodiment in claimed range of the present invention, and when the refractive index of probing medium changes between 1.0～1.05, the zero level efficiency of transmission of TM polarized light is with the curve of wavelength variations.

Fig. 3 is embodiment in Fig. 2, and when the refractive index of probing medium changes between 1.30～1.35, the zero level efficiency of transmission of TM polarized light is with the curve of wavelength variations.

TM polarization graphene nanobelt sensor array of the present invention, there is the advantages such as flexible and convenient to use, highly sensitive, quality factor is high, capable of dynamic is tuning, it is a kind of desirable senser element, utilize electron-beam direct writing device in conjunction with Microelectronic etching technique, can be in enormous quantities, produce at low cost, the sensor performance of making is stable, reliable, has important practical prospect.

Transducer sensitivity and quality factor during the incident of table 1 infrared band TM polarized light

Claims (2)

1. for a TM polarization graphene nanobelt sensor array for infrared band, the cycle that it is characterized in that the top graphene nanobelt array of this sensor is that 245～255 nanometers and dutycycle are 0.45～0.55, and Fermi level is 0.65～0.75eV.

2. TM polarization graphene nanobelt sensor array according to claim 1, is characterized in that cycle and the dutycycle of the top graphene nanobelt array of described sensor is respectively 250 nanometers and 0.5, and Fermi level is 0.7eV.

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