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High sensitivity biosensors based on germanium nanowires fabricated by Ge condensation technique
Materials Letters 172 (2016) 142–145
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
High sensitivity biosensors based on germanium nanowires fabricated by Ge condensation technique Lin Ye a,b, Qi Cai b, Baojian Xu b, Zengfeng Di b, Miao Zhang b, Jianhong Yang a,n a
School of Physical Science and Technology, Lanzhou University, Lanzhou 730000, China State Key Laboratory of Functional Materials for Informatics, Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
b
art ic l e i nf o
a b s t r a c t
Article history: Received 31 December 2015 Accepted 29 February 2016 Available online 2 March 2016
We demonstrate a novel technique to fabricate germanium nanowires (GeNWs) for field effect transistor biosensors. Arrays of core-shell structure GeNWs were “top-down” fabricated by combining the complementary metal-oxide semiconductor (CMOS) compatible technology and Ge condensation technology. The obtained GeNWs had stable SiO2 cladding, which acted as good modification platform for biochemical detection, since SiO2 modification was a mature technology. After the GeNWs were covalently bonded with DNA probe, the nanosensor demonstrated highly sensitive concentration-dependent current change in response to target DNA. This study may pave the way for further application such as the integration of bioelectronics and biosensors with the attractive semiconductor material Ge in future work. & 2016 Elsevier B.V. All rights reserved.
Keywords: Sensors Semiconductors Ge condensation
1. Introduction Over the years, biosensors based on nanoelectronic field-effect transistors (FETs) have attracted a great deal of attention for chemical and biological applications in the past decade. Among various nanostructures, SiNW has been applied in various biosensors. Since the first biosensors based on nanoelectronic FETs was demonstrated in 2001 [1], silicon nanowire field-effect transistor (SiNW-FET) biosensors [2,3] have been used for ultrasensitive, multiplexed real-time detection of a variety of biological species including protein disease biomarkers at a femtomolar level [4,5], DNA and DNA mismatch identification at the tens of femtomolar level [6], and ions detection or even single viruses [7]. Currently, with the rapid development of modern microelectronics, Ge has attracted significant interest as a good candidate to replace Si for future-generation microelectronics, owing to its better intrinsic properties that include narrower band gap, higher carrier mobilities and larger exciton Bohr radius [8]. However, the lack of stable surface including poor passivation, thermal instability, and even water soluble oxide of Ge has been a technology bottleneck in introducing Ge channels to biosensors. In this work, high quality GeNWs were fabricated utilizing “top-down” approach combined with Ge condensation technique [9]. During the Ge condensation process, by further oxidation of the starting SiGe wine at n
Corresponding author. E-mail address: [email protected] (J. Yang).
http://dx.doi.org/10.1016/j.matlet.2016.02.160 0167-577X/& 2016 Elsevier B.V. All rights reserved.
temperature lower than the melting point of Si1 xGex, a strained GeNW with SiO2 surrounded was realized. After fabrication of back-gate GeNW-FET device, detection of DNA molecule has been investigated. The modified nanosensor revealed high sensitivity for rapid and reliable detection of complementary target DNA with a detection limit of 5 fM.
2. Materials and methods 2.1. Fabrication and characterization of the GeNW Our fabrication procedure started with the SGOI substrate, which was produced by transferring of the 105 nm thick SiGe layer (Ge fraction x¼ 0.30) onto the oxide wafer, as described in our reported work [10]. Based on the SGOI wafer, the SiGe alloy layer was patterned and etched to form 180 nm wide fin structures with electron beam lithography (EBL) and reactive ion etching (RIE) processes. The obtained fin structures were firstly condensed at 950 °C to increase the Ge concentration to 65%, then decreased the condensation temperature to 825 °C to accomplish the rest condensation process and achieve the final GeNWs on insulator substrate. The GeNWs were characterized by high-resolution transmission electron microscopy (TEM, FET-Tecnai G2F20 S-7WIN) and Raman spectroscopy (HORIBA Jobin Yvon HR800).
L. Ye et al. / Materials Letters 172 (2016) 142–145
2.2. Fabrication and surface modification Subsequently, after the removal of the SiO2 cladding on the NW terminals with wet etching method, Ti/Au (10 nm/100 nm) bilayer was deposited and annealed at 300 °C in nitrogen ambient for 30 min to define source and drain electrodes. Finally, to match the requirements of biosensor application in aqueous conditions and avoid short-circuit between electrodes, a 50 nm passivation layer Si3N4 was deposited and the back-gate GeNW-FET biosensor was realized. Surface SiO2 can not only protect the NWs from oxidation corrosion but also could be employed as a good modification platform in biosensor applications. Firstly, prior to the chemical modification, the NWs were firstly cleaned with oxygen plasma treatment (100 W, 60 s) to obtain hydrophilic surface. Then the NWs were immersed in analytical grade (3-aminopropyl) triethoxysilane (APTES, 2% in absolute ethanol) solution overnight to realize the amine-terminated surface. To stabilize the bonded APTES self-assemble monolayer, the APTES-modified NWs were thoroughly washed with absolute ethanol and baked at 120 °C for 30 min. Following, glutaraldehyde (GLU) was utilized as the biofunctional cross-linker to covalently bind with the amine-terminated NWs surface. Through immersed in 2.5% GLU solution (in 1 PBS buffer) for 1 h at room temperature, the NWs were then thoroughly washed with the same buffer and dried with nitrogen. Then the surface functionalization process was studied through X-ray photoelectron spectroscopy (XPS). 2.3. DNA hybridization and electrochemical measurement Subsequently, the 5′-amine-terminated probe DNA in 1 PBS buffer was incubated with the NWs overnight at 4 °C to realize
143
probe DNA immobilization and the unreacted probe DNA molecules were removed and thoroughly washed with the blank buffer. Finally, after capture DNA probe immobilization, the hybridization solution containing target DNAs were introduced to the NWs respectively. The chosen target microRNA125a (miRNA125a) here is one of the biomarkers of lung cancer in early-stage. Electrical signals were collected at the same time.
3. Results and discussions 3.1. HRTEM analysis Fig. 1(a) illustrates the scheme of the two-steps Ge condensation process. The morphology and atoms concentration were characterized by cross-section HRTEM and EDX mapping in Fig. 1 (b). Firstly, the Si0.70Ge0.30 wire with width of about 180 nm was achieved by EBL and RIE processes. Si atoms distribute in Si0.70Ge0.30 wire and BOX layer, while Ge atoms mainly in the Si0.70Ge0.30 wire. Secondly, the obtained Si0.70Ge0.30 wires were condensed at 950 °C for 45 min to increase the Ge concentration to about 65%. Except remained Si atoms in the Si0.35Ge0.65, most of the Si atoms were oxidized to form the surface SiO2. The Si0.35Ge0.65 had smaller diameter and being covered with SiO2. Ge atoms were rejected from the surrounding SiO2 layers and concentrated in the Si0.35Ge0.65 wire. Finally, the condensation temperature was decreased to 825 °C and oxidation was stopped after all of Si atoms in the SiGe wire ware oxidized. Consequently, an 80 nm wide semicircle GeNW with SiO2 surrounded was obtained. From the EDX mapping in Fig. 1(b), the gradually light up blue color, which refers to the Ge atoms, illustrate the increase of Ge fraction. The nanostructure of obtained GeNWs was stable and had
Fig. 1. (a) Schematic illustration of the Ge condensation process. (b) Corresponding HRTEM cross-section images of the GeNW and EDX mapping of the Si and Ge atoms. The scale bars are 60 nm. (For interpretation of the references to color in this figure, the reader is referred to the web version of this article.)
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L. Ye et al. / Materials Letters 172 (2016) 142–145
Fig. 3. Comparison of XPS spectra of blank (black line) and APTES-modified SiO2 (blue line) on the GeNWs, the insets were high resolution comparison of N 1s state and C 1s state respectively. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
3.4. Biochemical detection Fig. 2. Raman spectra comparison of the NW during Ge condensation process.
excellent oxidation resistance for storage. 3.2. Raman analysis The Raman spectroscopy technique was used to confirm the Ge fraction x during the Ge condensation process. In Fig. 2, Raman spectra were collected for the three different steps in Fig. 1. The peaks marked I, II, III, and IV correspond to Ge-Ge mode, Si-Ge mode, Si-Si mode in SiGe layer, and Si-Si mode in the Si substrate, respectively. In the first stage, the value of Ge fraction before condensation was evaluated from the Raman signals of peaks I, II and III, which was about 0.30. After 950 °C condensation, the peaks of III disappeared, which means the value of Ge fraction was at least 0.65. Finally, since the peaks of II and III disappeared completely after 825 °C condensation, we confirm that GeNWs were formed. 3.3. XPS analysis The comparison XPS spectra of blank SiO2 (black) and APTESmodified SiO2 (blue) was displayed in Fig. 3. After the modification with APTES, significant changes assigned to C 1s and N 1s peaks were obtained. Here, these two elements C 1s and N 1s are able to differentiate the APTES modification step on SiO2 surface. In the high resolution XPS spectra for C 1s peaks (the right inset), starting with a reference sample of blank SiO2 surface, the weak peak was mainly due to the inevitable contamination from the ambient environment. Whereas the increased C 1s peak for APTES-SiO2 was contributed to the introduction of the propyl group present in APTES molecule. For N 1s peaks (the left inset), significant new peak around 400 eV was observed due to the binding of amine group of the silane molecule. In addition, the broad peak was attributed to two components, one at 400 eV due to the free amine (–NH2) of the aminosiloxane and the second at 402 eV due to the protonated nitrogen state (–NH3 þ ). These measurements provide clear evidence that the GeNW surface has been chemically modified with APTES.
The functionalization principle of the core-shell NW biosensor was illustrated in Fig. 4a. GLU binding was achieved through its aldehyde group (–CHO) that ensured a covalent bond with the amino group of APTES. For probe immobilization, 5′-amine-terminated probe DNA molecules were linked to the rest –CHO on the NW surface. The hybridization buffer containing target DNA was finally introduced to the NWs for hybridization reaction. After hybridization reaction, the corresponding transfer characteristic curves were collected in Fig. 4(b). Herein, the DNA probe immobilized NW was used as reference, due to the concentrationdependent hybridization reaction, the negatively charged DNA sequence was bound to surface SiO2, resulting in the accumulation of carriers and an increase in current. To obtain a more quantitative analysis, the experimental results were calibrated and the sensitivity (S) of the device for target DNA detection was defined as:
S=
I′ − I0 . I0
Where I0 and I′ were the current in the NW arrays before and after DNA hybridization reaction, respectively. The values of S for different concentrations were collected in Fig. 4(c) at VG ¼2.9 V, since the sensitivity of NW-FET sensors can be exponentially enhanced in the subthreshold region [11]. The limit of detection (LOD) of this nanosensor was calculated to be 5 fM from a sensor response that was equal to three times the standard deviation of the baseline noise, suggesting good potential in label-free DNA hybridization detection with high sensitivity.
4. Conclusion In summary, the GeNWs coated with SiO2 were fabricated by combining a CMOS-compatible method and Ge condensation technology, which was promising in the mass production of NW devices. The nanostructure of obtained GeNW was stable and had excellent oxidation resistance for storage. Surface SiO2 acted as good modification platform for biochemical detection, since SiO2 modification was a mature technology. The fabricated nanosensor revealed high sensitivity for rapid and reliable detection of cancer
L. Ye et al. / Materials Letters 172 (2016) 142–145
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Fig. 4. (a) Schematic illustration for DNA hybridization on the Ge-SiO2 core-shell NW surface. (b) Concentration-dependent electrical response of the nanosensor for target DNA. (c) S factor versus logarithm of target DNA concentration at VG ¼ 2.9 V, the inset shows the detection limit.
biomarker, the detection limit was calculated to be 5 fM. Our preliminary biosensor applications may present the potential in the further development of GeNWs in bioelectronics.
References [1] Y. Cui, Q.Q. Wei, H.K. Park, C.M. Lieber, Science 293 (2001) 1289–1292. [2] F. Patolsky, C.M. Lieber, Mater. Today 8 (2005) 20–28. [3] F. Patolsky, G. Zheng, C.M. Lieber, Nanomedicine 1 (2006) 51–65.
[4] G.F. Zheng, F. Patolsky, Y. Cui, W.U. Wang, C.M. Lieber, Nat. Biotechnol. 23 (2005) 1294–1301. [5] E. Stern, A. Vacic, N.K. Rajan, J.M. Criscione, J. Park, B.R. Ilic, D.J. Mooney, M. A. Reed, T.M. Fahmy, Nat. Nanotechnol. 5 (2010) 138–142. [6] J. Hahm, C.M. Lieber, Nano Lett. 4 (2004) 51–54. [7] F. Patolsky, G.F. Zheng, O. Hayden, M. Lakadamyali, X.W. Zhuang, C.M. Lieber, Proc. Natl. Acad. Sci. USA 101 (2004) 14017–14022. [8] L.Z. Pei, Z.Y. Cai, Recent Pat. Nanotechnol. 6 (2012) 44–59. [9] W.T. Lai, P.W. Li, Nanotechnology 18 (2007) 145402. [10] L. Ye, M. Zhang, Z.Y. Xue, J.H. Yang, X. Wang, Z.F. Di, Appl. Surf. Sci. 356 (2015) 1052–1057. [11] X.P.A. Gao, G.F. Zheng, C.M. Lieber, Nano Lett. 10 (2010) 547–552.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
High sensitivity biosensors based on germanium nanowires fabricated by Ge condensation technique Lin Ye a,b, Qi Cai b, Baojian Xu b, Zengfeng Di b, Miao Zhang b, Jianhong Yang a,n a
School of Physical Science and Technology, Lanzhou University, Lanzhou 730000, China State Key Laboratory of Functional Materials for Informatics, Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
b
art ic l e i nf o
a b s t r a c t
Article history: Received 31 December 2015 Accepted 29 February 2016 Available online 2 March 2016
We demonstrate a novel technique to fabricate germanium nanowires (GeNWs) for field effect transistor biosensors. Arrays of core-shell structure GeNWs were “top-down” fabricated by combining the complementary metal-oxide semiconductor (CMOS) compatible technology and Ge condensation technology. The obtained GeNWs had stable SiO2 cladding, which acted as good modification platform for biochemical detection, since SiO2 modification was a mature technology. After the GeNWs were covalently bonded with DNA probe, the nanosensor demonstrated highly sensitive concentration-dependent current change in response to target DNA. This study may pave the way for further application such as the integration of bioelectronics and biosensors with the attractive semiconductor material Ge in future work. & 2016 Elsevier B.V. All rights reserved.
Keywords: Sensors Semiconductors Ge condensation
1. Introduction Over the years, biosensors based on nanoelectronic field-effect transistors (FETs) have attracted a great deal of attention for chemical and biological applications in the past decade. Among various nanostructures, SiNW has been applied in various biosensors. Since the first biosensors based on nanoelectronic FETs was demonstrated in 2001 [1], silicon nanowire field-effect transistor (SiNW-FET) biosensors [2,3] have been used for ultrasensitive, multiplexed real-time detection of a variety of biological species including protein disease biomarkers at a femtomolar level [4,5], DNA and DNA mismatch identification at the tens of femtomolar level [6], and ions detection or even single viruses [7]. Currently, with the rapid development of modern microelectronics, Ge has attracted significant interest as a good candidate to replace Si for future-generation microelectronics, owing to its better intrinsic properties that include narrower band gap, higher carrier mobilities and larger exciton Bohr radius [8]. However, the lack of stable surface including poor passivation, thermal instability, and even water soluble oxide of Ge has been a technology bottleneck in introducing Ge channels to biosensors. In this work, high quality GeNWs were fabricated utilizing “top-down” approach combined with Ge condensation technique [9]. During the Ge condensation process, by further oxidation of the starting SiGe wine at n
Corresponding author. E-mail address: [email protected] (J. Yang).
http://dx.doi.org/10.1016/j.matlet.2016.02.160 0167-577X/& 2016 Elsevier B.V. All rights reserved.
temperature lower than the melting point of Si1 xGex, a strained GeNW with SiO2 surrounded was realized. After fabrication of back-gate GeNW-FET device, detection of DNA molecule has been investigated. The modified nanosensor revealed high sensitivity for rapid and reliable detection of complementary target DNA with a detection limit of 5 fM.
2. Materials and methods 2.1. Fabrication and characterization of the GeNW Our fabrication procedure started with the SGOI substrate, which was produced by transferring of the 105 nm thick SiGe layer (Ge fraction x¼ 0.30) onto the oxide wafer, as described in our reported work [10]. Based on the SGOI wafer, the SiGe alloy layer was patterned and etched to form 180 nm wide fin structures with electron beam lithography (EBL) and reactive ion etching (RIE) processes. The obtained fin structures were firstly condensed at 950 °C to increase the Ge concentration to 65%, then decreased the condensation temperature to 825 °C to accomplish the rest condensation process and achieve the final GeNWs on insulator substrate. The GeNWs were characterized by high-resolution transmission electron microscopy (TEM, FET-Tecnai G2F20 S-7WIN) and Raman spectroscopy (HORIBA Jobin Yvon HR800).
L. Ye et al. / Materials Letters 172 (2016) 142–145
2.2. Fabrication and surface modification Subsequently, after the removal of the SiO2 cladding on the NW terminals with wet etching method, Ti/Au (10 nm/100 nm) bilayer was deposited and annealed at 300 °C in nitrogen ambient for 30 min to define source and drain electrodes. Finally, to match the requirements of biosensor application in aqueous conditions and avoid short-circuit between electrodes, a 50 nm passivation layer Si3N4 was deposited and the back-gate GeNW-FET biosensor was realized. Surface SiO2 can not only protect the NWs from oxidation corrosion but also could be employed as a good modification platform in biosensor applications. Firstly, prior to the chemical modification, the NWs were firstly cleaned with oxygen plasma treatment (100 W, 60 s) to obtain hydrophilic surface. Then the NWs were immersed in analytical grade (3-aminopropyl) triethoxysilane (APTES, 2% in absolute ethanol) solution overnight to realize the amine-terminated surface. To stabilize the bonded APTES self-assemble monolayer, the APTES-modified NWs were thoroughly washed with absolute ethanol and baked at 120 °C for 30 min. Following, glutaraldehyde (GLU) was utilized as the biofunctional cross-linker to covalently bind with the amine-terminated NWs surface. Through immersed in 2.5% GLU solution (in 1 PBS buffer) for 1 h at room temperature, the NWs were then thoroughly washed with the same buffer and dried with nitrogen. Then the surface functionalization process was studied through X-ray photoelectron spectroscopy (XPS). 2.3. DNA hybridization and electrochemical measurement Subsequently, the 5′-amine-terminated probe DNA in 1 PBS buffer was incubated with the NWs overnight at 4 °C to realize
143
probe DNA immobilization and the unreacted probe DNA molecules were removed and thoroughly washed with the blank buffer. Finally, after capture DNA probe immobilization, the hybridization solution containing target DNAs were introduced to the NWs respectively. The chosen target microRNA125a (miRNA125a) here is one of the biomarkers of lung cancer in early-stage. Electrical signals were collected at the same time.
3. Results and discussions 3.1. HRTEM analysis Fig. 1(a) illustrates the scheme of the two-steps Ge condensation process. The morphology and atoms concentration were characterized by cross-section HRTEM and EDX mapping in Fig. 1 (b). Firstly, the Si0.70Ge0.30 wire with width of about 180 nm was achieved by EBL and RIE processes. Si atoms distribute in Si0.70Ge0.30 wire and BOX layer, while Ge atoms mainly in the Si0.70Ge0.30 wire. Secondly, the obtained Si0.70Ge0.30 wires were condensed at 950 °C for 45 min to increase the Ge concentration to about 65%. Except remained Si atoms in the Si0.35Ge0.65, most of the Si atoms were oxidized to form the surface SiO2. The Si0.35Ge0.65 had smaller diameter and being covered with SiO2. Ge atoms were rejected from the surrounding SiO2 layers and concentrated in the Si0.35Ge0.65 wire. Finally, the condensation temperature was decreased to 825 °C and oxidation was stopped after all of Si atoms in the SiGe wire ware oxidized. Consequently, an 80 nm wide semicircle GeNW with SiO2 surrounded was obtained. From the EDX mapping in Fig. 1(b), the gradually light up blue color, which refers to the Ge atoms, illustrate the increase of Ge fraction. The nanostructure of obtained GeNWs was stable and had
Fig. 1. (a) Schematic illustration of the Ge condensation process. (b) Corresponding HRTEM cross-section images of the GeNW and EDX mapping of the Si and Ge atoms. The scale bars are 60 nm. (For interpretation of the references to color in this figure, the reader is referred to the web version of this article.)
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L. Ye et al. / Materials Letters 172 (2016) 142–145
Fig. 3. Comparison of XPS spectra of blank (black line) and APTES-modified SiO2 (blue line) on the GeNWs, the insets were high resolution comparison of N 1s state and C 1s state respectively. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
3.4. Biochemical detection Fig. 2. Raman spectra comparison of the NW during Ge condensation process.
excellent oxidation resistance for storage. 3.2. Raman analysis The Raman spectroscopy technique was used to confirm the Ge fraction x during the Ge condensation process. In Fig. 2, Raman spectra were collected for the three different steps in Fig. 1. The peaks marked I, II, III, and IV correspond to Ge-Ge mode, Si-Ge mode, Si-Si mode in SiGe layer, and Si-Si mode in the Si substrate, respectively. In the first stage, the value of Ge fraction before condensation was evaluated from the Raman signals of peaks I, II and III, which was about 0.30. After 950 °C condensation, the peaks of III disappeared, which means the value of Ge fraction was at least 0.65. Finally, since the peaks of II and III disappeared completely after 825 °C condensation, we confirm that GeNWs were formed. 3.3. XPS analysis The comparison XPS spectra of blank SiO2 (black) and APTESmodified SiO2 (blue) was displayed in Fig. 3. After the modification with APTES, significant changes assigned to C 1s and N 1s peaks were obtained. Here, these two elements C 1s and N 1s are able to differentiate the APTES modification step on SiO2 surface. In the high resolution XPS spectra for C 1s peaks (the right inset), starting with a reference sample of blank SiO2 surface, the weak peak was mainly due to the inevitable contamination from the ambient environment. Whereas the increased C 1s peak for APTES-SiO2 was contributed to the introduction of the propyl group present in APTES molecule. For N 1s peaks (the left inset), significant new peak around 400 eV was observed due to the binding of amine group of the silane molecule. In addition, the broad peak was attributed to two components, one at 400 eV due to the free amine (–NH2) of the aminosiloxane and the second at 402 eV due to the protonated nitrogen state (–NH3 þ ). These measurements provide clear evidence that the GeNW surface has been chemically modified with APTES.
The functionalization principle of the core-shell NW biosensor was illustrated in Fig. 4a. GLU binding was achieved through its aldehyde group (–CHO) that ensured a covalent bond with the amino group of APTES. For probe immobilization, 5′-amine-terminated probe DNA molecules were linked to the rest –CHO on the NW surface. The hybridization buffer containing target DNA was finally introduced to the NWs for hybridization reaction. After hybridization reaction, the corresponding transfer characteristic curves were collected in Fig. 4(b). Herein, the DNA probe immobilized NW was used as reference, due to the concentrationdependent hybridization reaction, the negatively charged DNA sequence was bound to surface SiO2, resulting in the accumulation of carriers and an increase in current. To obtain a more quantitative analysis, the experimental results were calibrated and the sensitivity (S) of the device for target DNA detection was defined as:
S=
I′ − I0 . I0
Where I0 and I′ were the current in the NW arrays before and after DNA hybridization reaction, respectively. The values of S for different concentrations were collected in Fig. 4(c) at VG ¼2.9 V, since the sensitivity of NW-FET sensors can be exponentially enhanced in the subthreshold region [11]. The limit of detection (LOD) of this nanosensor was calculated to be 5 fM from a sensor response that was equal to three times the standard deviation of the baseline noise, suggesting good potential in label-free DNA hybridization detection with high sensitivity.
4. Conclusion In summary, the GeNWs coated with SiO2 were fabricated by combining a CMOS-compatible method and Ge condensation technology, which was promising in the mass production of NW devices. The nanostructure of obtained GeNW was stable and had excellent oxidation resistance for storage. Surface SiO2 acted as good modification platform for biochemical detection, since SiO2 modification was a mature technology. The fabricated nanosensor revealed high sensitivity for rapid and reliable detection of cancer
L. Ye et al. / Materials Letters 172 (2016) 142–145
145
Fig. 4. (a) Schematic illustration for DNA hybridization on the Ge-SiO2 core-shell NW surface. (b) Concentration-dependent electrical response of the nanosensor for target DNA. (c) S factor versus logarithm of target DNA concentration at VG ¼ 2.9 V, the inset shows the detection limit.
biomarker, the detection limit was calculated to be 5 fM. Our preliminary biosensor applications may present the potential in the further development of GeNWs in bioelectronics.
References [1] Y. Cui, Q.Q. Wei, H.K. Park, C.M. Lieber, Science 293 (2001) 1289–1292. [2] F. Patolsky, C.M. Lieber, Mater. Today 8 (2005) 20–28. [3] F. Patolsky, G. Zheng, C.M. Lieber, Nanomedicine 1 (2006) 51–65.
[4] G.F. Zheng, F. Patolsky, Y. Cui, W.U. Wang, C.M. Lieber, Nat. Biotechnol. 23 (2005) 1294–1301. [5] E. Stern, A. Vacic, N.K. Rajan, J.M. Criscione, J. Park, B.R. Ilic, D.J. Mooney, M. A. Reed, T.M. Fahmy, Nat. Nanotechnol. 5 (2010) 138–142. [6] J. Hahm, C.M. Lieber, Nano Lett. 4 (2004) 51–54. [7] F. Patolsky, G.F. Zheng, O. Hayden, M. Lakadamyali, X.W. Zhuang, C.M. Lieber, Proc. Natl. Acad. Sci. USA 101 (2004) 14017–14022. [8] L.Z. Pei, Z.Y. Cai, Recent Pat. Nanotechnol. 6 (2012) 44–59. [9] W.T. Lai, P.W. Li, Nanotechnology 18 (2007) 145402. [10] L. Ye, M. Zhang, Z.Y. Xue, J.H. Yang, X. Wang, Z.F. Di, Appl. Surf. Sci. 356 (2015) 1052–1057. [11] X.P.A. Gao, G.F. Zheng, C.M. Lieber, Nano Lett. 10 (2010) 547–552.