Alan Iacopi - Academia.edu (original) (raw)

Papers by Alan Iacopi

2018 IEEE Micro Electro Mechanical Systems (MEMS), 2018

This work presents the fabrication, mechanical strength characterization, and cell culture demons... more This work presents the fabrication, mechanical strength characterization, and cell culture demonstration of a high aspect ratio silicon carbide (SiC) membrane. Optimizations in the deposition and fabrication make an ultra-high aspect ratio up to 20,000 SiC membranes with high fracture strength possible. Utilizing the superior properties of SiC material, the ultra-thin SiC membrane is a promising for cell culture/stretching devices, enabling very short optical accesses. The biocompatibility of the SiC membrane was confirmed with the 3T3 fibroblasts cell viability rate of 92.7%, in which the cells flattened and elongated their morphology while maintaining a strong adhesion to the SiC surface.

L'invention concerne de maniere generale, selon des modes de realisation, des semi-conducteur... more L'invention concerne de maniere generale, selon des modes de realisation, des semi-conducteurs et des techniques de fabrication de semi-conducteurs et, plus particulierement, des dispositifs, des circuits integres, des substrats, des tranches et des procedes pour former des structures de film afin de faciliter la formation d'epitaxie de carbure de silicium sur un substrat, tel qu'un substrat a base de silicium. Dans certains modes de realisation, un procede de preparation d'un substrat pour la formation de couches epitaxiales de carbure de silicium peut comprendre la formation d'une couche ultramince d'oxyde qui est configuree pour empecher les contaminants d'interagir avec un substrat a base de silicium. En outre, le procede peut comprendre la formation d'un film carbone sur le substrat a base de silicium qui est configure pour empecher les contaminants d'interagir avec le substrat a base de silicium. Le film carbone peut etre configure pour etre...

Sustainable Design and Manufacturing 2018, 2018

This paper demonstrates the prospect of using a 3C-SiC/Si heterostructure as an ultraviolet and v... more This paper demonstrates the prospect of using a 3C-SiC/Si heterostructure as an ultraviolet and visible photodetector. The heterojunction has been grown epitaxially on Si-substrate via a Low Pressure Chemical Vapor Deposition technique at 1000 C. The detector shows a good diode characteristic with a rectification ratio of 1.03×10 3 and a reverse leakage current of 7.2×10-6 A at 2V in dark conditions. The responsivity of the device is found to be 5.4×10-2 A/W and 3.18×10-2 A/W at a reverse bias of 2V under visible (635 nm) and UV (375 nm) illumination, respectively. An energy band diagram is proposed to explain the photosensitivity of the heterostructure.

physica status solidi (b), 2021

This article has been accepted for publication and undergone full peer review but has not been th... more This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as

RSC Advances, 2018

The piezoresistance in crystalline 3C-SiC epitaxially grown on Si was investigated at low tempera... more The piezoresistance in crystalline 3C-SiC epitaxially grown on Si was investigated at low temperatures down to 150 K. The large gauge factor in 3C-SiC indicates its feasibility for sensing applications in cryogenic environments.

Journal of Instrumentation, 2018

Silicon Nitride (SiN) membranes have long been the substrate of choice for many different synchro... more Silicon Nitride (SiN) membranes have long been the substrate of choice for many different synchrotron techniques at very different wavelengths (from IR to hard x-rays), due to their ease of production, relative robustness even in films <200 nm in thickness, and compatibility with standard microfabrication techniques. Here we present a set of data referring to custom-made Silicon Carbide (SiC) windows. We measured SiC surface roughness, mechanical robustness and membrane transmission both at IR and soft x-rays wavelengths, and compared the data with standard Si3N4, acquired in the same conditions. Further, we grew HEK293T cells both on Si3N4 and SiC membranes, and analysed them with IR and soft X-ray microscopy. Our data demonstrates how SiC is an excellent choice as membrane material for synchrotron measurements, since it shows higher transmission and higher robustness as compared to Si3N4 of the same thickness, and an improved compatibility for cell culturing, allowing to postulate their use also for bio-oriented research.

IEEE Electron Device Letters, 2019

Silicon carbide (SiC) has been extensively investigated in the last decade, specifically for appl... more Silicon carbide (SiC) has been extensively investigated in the last decade, specifically for applications in harsh environments. However, most SiC sensors require an external power supply which cannot operate at high temperatures. This work develops a new sensing technology in a SiC platform based on near field communication to eliminate the requirement for wired power sources. 3C-SiC temperature sensors were fabricated from a SiC-on-insulator substrate formed by anodic bonding. The sensors functioned based on the thermoresistance of the SiC films with the high TCR of-13,000 ppm/K at 300 K and-3,000 ppm/K at 600 K. The change in the resistance of the SiC sensors was wirelessly measured using a reading coil placed outside of the heating chamber, showing a significant shift in the resonant frequency (-400 ppm/K at 600 K) of the couplingimpedance under the variation of temperatures. The proposed technique is promising for the development of wireless wideband-gap sensors used in extreme conditions.

Materials Letters, 2018

The pseudo-Hall effect in n-type single crystal 3C-SiC(1 0 0) with low carrier concentration has ... more The pseudo-Hall effect in n-type single crystal 3C-SiC(1 0 0) with low carrier concentration has been investigated. Low pressure chemical vapor deposition was used to grow the single crystal n-type 3C-SiC(1 0 0) and Hall devices were fabricated by photolithography and dry etch processes. A large pseudo-Hall effect was observed in the grown thin films which showed a strong dependence on the crystallographic orientation. N-type 3C-SiC(1 0 0) with low carrier concentration shows a completely different behavior of pseudo-Hall measurements as compared to the p-type 3C-SiC(1 0 0). Contrary to p-type, the effect is maximum along [1 0 0] crystallographic orientation and minimum along [1 1 0] orientation. Moreover, the observed pseudo-Hall effect is 50% larger than p-type with higher carrier concentration grown by the same process which makes n-type 3C-SiC(1 0 0) with low carrier concentration more suitable material for designing highly sensitive micro-mechanical sensors.

physica status solidi (a), 2018

Scientific Reports, 2017

This work examines the stability of epitaxial 3C-SiC/Si heterojunctions subjected to heat treatme... more This work examines the stability of epitaxial 3C-SiC/Si heterojunctions subjected to heat treatments between 1000 °C and 1300 °C. Because of the potential for silicon carbide in high temperature and harsh environment applications, and the economic advantages of growing the 3C-SiC polytype on large diameter silicon wafers, its stability after high temperature processing is an important consideration. Yet recently, this has been thrown into question by claims that the heterojunction suffers catastrophic degradation at temperatures above 1000 °C. Here we present results showing that the heterojunction maintains excellent diode characteristics following heat treatment up to 1100 °C and while some changes were observed between 1100 °C and 1300 °C, diodes maintained their rectifying characteristics, enabling compatibility with a large range of device fabrication. The parameters of as-grown diodes were J0 = 1 × 10−11 A/mm2, n = 1.02, and +/−2V rectification ratio of 9 × 106. Capacitance an...

Advanced Engineering Materials, 2017

This work presents fabrication of micro structures on sub-100 nm SiC membranes with a large aspec... more This work presents fabrication of micro structures on sub-100 nm SiC membranes with a large aspect ratio up to 1:3200. Unlike conventional processes, this approach starts with Si wet etching to form suspended SiC membranes, followed by micro-machined processes to pattern free-standing microstructures such as cantilevers and micro bridges. This technique eliminates the sticking or the under-etching effects on free-standing structures, enhancing mechanical performance which is favorable for MEMS applications. In addition, post-Si-etching photography also enables the formation of metal electrodes on free standing SiC membranes to develop electrically-measurable devices. To proof this concept, the authors demonstrate a SiC pressure sensor by applying lithography and plasma etching on released ultrathin SiC films. The sensors exhibit excellent linear response to the applied pressure, as well as good repeatability. The proposed method opens a pathway for the development of self-sensing free-standing SiC sensors.

ACS applied materials & interfaces, Jan 6, 2017

Micromachined membranes are promising platforms for cell culture thanks to their miniaturization ... more Micromachined membranes are promising platforms for cell culture thanks to their miniaturization and integration capabilities. Possessing chemical inertness, biocompatibility, and integration, silicon carbide (SiC) membranes have attracted great interest toward biological applications. In this paper, we present the batch fabrication, mechanical characterizations, and cell culture demonstration of robust ultrathin epitaxial deposited SiC membranes. The as-fabricated ultrathin SiC membranes, with an ultrahigh aspect ratio (length/thickness) of up to 20 000, possess high a fracture strength up to 2.95 GPa and deformation up to 50 μm. A high optical transmittance of above 80% at visible wavelengths was obtained for 50 nm membranes. The as-fabricated membranes were experimentally demonstrated as an excellent substrate platform for bio-MEMS/NEMS cell culture with the cell viability rate of more than 92% after 72 h. The ultrathin SiC membrane is promising for in vitro observations/imaging ...

Micromachines, 2017

We report on the radio frequency (RF) sputtering of c-axis oriented ZnO thin films on top of epit... more We report on the radio frequency (RF) sputtering of c-axis oriented ZnO thin films on top of epitaxial 3C-SiC-on-Si (111) substrates, which were then subjected to post-annealing treatment at 400, 600 and 800 • C. Grazing incident X-ray Diffraction (XRD) data show that the Full Width Half Maximum (FWHM) values for O 2 /Ar ratios between 30% and 60% are consistent, with a mean of 0.325 • and a standard deviation of 0.03 •. This is largely attributed to the smaller lattice mismatch of 5% between the ZnO (002) and SiC (111) films. The quality of the ZnO films deteriorated at the post-annealing treatment of 800 • C, as demonstrated by the increasing value of FWHM diffraction peaks, the reducing value of the peak intensity, the reducing percentage of (002) oriented area under the curve, and the increasing value of biaxial stress. We propose a simple growth model to explain the result.

Applied Physics Letters, 2017

Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena, 2017

This article reports on the direct current sputtering of AlN thin films on top of a cubic-silicon... more This article reports on the direct current sputtering of AlN thin films on top of a cubic-silicon carbide (111) on silicon (111) substrates. The authors varied the nitrogen (N 2) concentrations, while keeping other process parameters fixed at the power of 1200 W, the substrate temperature of 350 C, the target to substrate distance of 20 cm, and the sputtering pressure of 2 mT. The total N 2 /Ar gas flow is 50 sccm, and the poison mode starts at 40%. The x-ray diffraction results show that the AlN films are highly oriented along the (002) orientation at various N 2 concentrations. The values of the three parameters support this observation, namely, (1) the extracted full width at half maximum (FWHM) of (002) diffraction peaks with the median of 0.28 and the standard deviation of 0.012 , (2) the area of AlN (002) under the curve is between 92% and 97%, and (3) the grain sizes are between 30.11 and 32.3 nm. The omega scan rocking curve of two samples at 40% and 80% N 2 concentrations depicts good quality AlN (002) films with the FWHM values of 1.5 and 2 , respectively. The relationship between the N 2 concentrations and the film's properties is elucidated. Finally, the authors discuss the effect of the lattice mismatch of 1% between AlN (002) and 3C-SiC (111). V

Journal of Crystal Growth, 2016

Aluminum Nitride (AlN) thin films are successfully deposited on epitaxial 3C-SiC-on-Si (100) subs... more Aluminum Nitride (AlN) thin films are successfully deposited on epitaxial 3C-SiC-on-Si (100) substrates using DC magnetron sputterer. The sputtered films are characterized on the following parameters: crystal orientations (Siemens D500 X-Ray diffraction tool), deposition rate (Nanospec AFT 180), surface roughness (Park NX20 Atomic Force Microscopy), refractive index (Rudolph AutoEL IV Ellipsometer), in-plane stress (Tencor Flexus 2320 System) and Raman Spectra (Rennishaw InVia Spectrometer). XRD results demonstrate that the orientation of the AlN thin films can be changed from (002) to (101) by increasing the Nitrogen to Argon ratio from 40% to 80% at the total gas flow of 50 sccm. We are also able to tune the in-plane stress via RF biasing on the substrate. Both controlling abilities enable the applications of these thin films for low cost longitudinal piezoelectric devices and a quasi-shear mode devices using (002) and (101) orientations, respectively.

ACS applied materials & interfaces, Jan 23, 2017

Single-crystal cubic silicon carbide has attracted great attention for MEMS and electronic device... more Single-crystal cubic silicon carbide has attracted great attention for MEMS and electronic devices. However, current leakage at the SiC/Si junction at high temperatures and visible-light absorption of the Si substrate are main obstacles hindering the use of the platform in a broad range of applications. To solve these bottlenecks, we present a new platform of single crystal SiC on an electrically insulating and transparent substrate using an anodic bonding process. The SiC thin film was prepared on a 150 mm Si with a surface roughness of 7 nm using LPCVD. The SiC/Si wafer was bonded to a glass substrate and then the Si layer was completely removed through wafer polishing and wet etching. The bonded SiC/glass samples show a sharp bonding interface of less than 15 nm characterized using deep profile X-ray photoelectron spectroscopy, a strong bonding strength of approximately 20 MPa measured from the pulling test, and relatively high optical transparency in the visible range. The trans...

Key Engineering Materials, 2017

This article reports the first results on stress induced pseudo-Hall effect in single crystal n-t... more This article reports the first results on stress induced pseudo-Hall effect in single crystal n-type 3C-SiC(100) grown by LPCVD process. After the growth process, Hall devices were fabricated by standard photolithography and dry etching processes. The bending beam method was employed to study the stress induced changes in the electrical response of the fabricated Hall devices. It has been observed that when stress is applied to the 3C-SiC(100) Hall devices, the offset voltage of the Hall devices varies linearly with the applied compressive and tensile stresses which is called, the pseudo-Hall effect. The variation of the offset voltage of these Hall devices is also proportional to the applied input current. This variation of the offset voltage with the applied compressive and tensile stresses shows that single crystal n-type 3C-SiC(100) can be used for stress sensing applications.

Materials Science Forum, 2016

In this paper, we present surprising MOS capacitor C–V bias instability observed in NO-grown oxid... more In this paper, we present surprising MOS capacitor C–V bias instability observed in NO-grown oxides, with distinctly different behavior compared to that of conventional NO-annealed oxides on 4H-SiC. Using sequential back-and-forth and bias-temperature stress C–V measurements, it was demonstrated that the C–V shift direction of NO-grown oxides was opposite to that of NO-annealed oxides. A model based on bias-temperature stress orientated near-interfacial dipoles is proposed to explain this unique behavior of NO-grown oxides.

RSC Adv., 2016

The unique growth mechanism of alternating supply epitaxy enables uniform 3C-SiC to be deposited ... more The unique growth mechanism of alternating supply epitaxy enables uniform 3C-SiC to be deposited on multiple large-diameter Si wafers.