Thin films Archives – Institute of Nano Electronic Engineering

Abstract – This paper investigates the influence of substrate-gate coupling on the ZnO-FET biosensor’s sensitivity for detection of cardiac troponin I (cTnI), a ‘gold standard’ biomarker for acute myocardial infarction (AMI). The FET-based device with introduction of substrate-gate coupling on p-type silicon-on-insulator (SOI) substrate is fabricated using conventional lithography processes. An n-type zinc oxide (ZnO) thin film deposited via electron-beam evaporator is used as transducer for bridging the source and drain regions. Surface modifications via functionalization with 3-aminopropyltriethoxysilane (APTES) and glutaraldehyde (GA) as chemical linkers, followed by immobilization of cTnI monoclonal antibody (MAb-cTnI) as bio-receptor on the ZnO thin film allow different concentration of cTnI detection with high selectivity. The device’s sensitivity increases up to 9 %•(g/ml)-1 with the increase of the substrate-gate voltage (VSG) up to -10 V at very low limit of detection (LOD) down to 1.6 fg/ml.

Corresponding Author: Mohamad Faris Mohamad Fathil
Corresponding Author’s Email: mohamadfaris@unimap.edu.my

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Abstract – Nanocrystalline Ge1-xSnx thin films have been formed after rapid thermal annealing of sputtered GeSn layers. The alloy films were deposited onto the Silicon (100) substrate via low cost radio frequency magnetron sputtering. Then, the films were annealed by rapid thermal annealing at 350 °C, 400 °C, and 450 °C for 10 s. The morphological, structural, and optical properties of the layers were investigated with field emission scanning electron microscopy (FESEM), Energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, and high-resolution X-ray diffraction (HR-XRD). The Raman analysis showed that the only observed phonon mode is attributed to Ge-Ge vibrations. Raman phonon intensities of GeSn thin films were enhanced with increasing the annealing temperature. The results clearly revealed that by increasing the annealing temperature the crystalline quality of the films were improved. The XRD measurements revealed the nanocrystalline phase formation in the annealed films with (111) preferred orientation. The results showed the potentiality of using the sputtering technique and rapid thermal anneal to produce crystalline GeSn layer.

Keywords – Germanium-tin, HR-XRD, Nanocrystalline materials, Raman spectroscopy, Sputtering, Thin films

Corresponding Author: Uda Hashim
Corresponding Author’s Email: uda@unimap.edu.my

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The ZnO-FET Biosensor for Cardiac Troponin I

Formation of nanocrystalline GeSn thin film on Si substrate by sputtering and rapid thermal annealing