Optical absorption sensing with dual-spectrum silicon LEDs in SOI-CMOS technology

Silicon p-n junction diodes emit low-intensity, broad-spectrum light near 1120 nm in forward bias and between 400-900 nm in reverse bias (avalanche). For the first time, we experimentally achieve optical absorption sensing of pigment in solution with silicon micro LEDs designed in a standard silicon-on-insulator CMOS technology. By driving a single LED in both forward and avalanche modes of operation, we steer it's electroluminescent spectrum between visible and near-infrared (NIR). We then characterize the vertical optical transmission of both visible and NIR light from the LED through the same micro-droplet specimen to a vertically mounted discrete silicon photodiode. The effective absorption coefficient of carmine solution in glycerol at varying concentrations were extracted from the color ratio in optical coupling. By computing the LED-specific molar absorption coefficient of carmine, we estimate the concentration (∼0.040 mol L-1) and validate the same with a commercial spectrophotometer (∼0.030 mol L-1). With a maximum observed sensitivity of ∼1260 cm-1mol-1L, the sensor is a significant step forward towards low-cost CMOS-integrated optical sensors with silicon LED as the light source intended for biochemical analyses in food sector and plant/human health. Accepted Author ManuscriptDynamics of Micro and Nano System

Optical sensing of chlorophyll(in) with dual-spectrum Si LEDs in SOI-CMOS technology

Small and low-cost chlorophyll sensors are popular in agricultural sector and food-quality control.Combining such sensors with silicon CMOS electronics is challenged by the absence of silicon-integrated light-sources.We experimentally achieve optical absorption sensing of chlorophyll based pigments with silicon (Si) micro light-emitting diodes (LED) as light-source, fabricated in a standard SOI-CMOS technology.By driving a Si LED in both forward and avalanche modes of operation,we steer its electroluminescentspectrum between visible (400-900 nm) and near-infrared (1120 nm). For detection of chlorophyll in solution phase, the dualspectrum light from the LED propagates vertically through glycerol micro-droplets containing sodium copper chlorophyllin at varying relative concentrations. The transmitted light is detected via an off-chip Si photodiode. The visible to near-infrared color ratio (COR) of the photocurrent yields the effective absorption coefficient. We introduce the LED-specificmolar absorption coefficient as ametric to compute the absolute pigment concentration (0.019 ± 0.006 mol L-1) and validate the results by measurements with a hybrid spectrophotometer. With the same sensor, we also show noninvasive monitoring of chlorophyll in plant leaves. COR sensitivities $\sim 3.9 \times 10^{4}$ mol-1L and $\sim 5.3 \times 10^{4}$ mol-1L are obtained for two leaf species, where light from the LED propagates diffusely through the thickness of the leaf prior to detection by the photodiode. Our work demonstrates the feasibility of realizing fully CMOS-integrated optical sensors for biochemical analyses in food sector and plant/human health.Accepted Author ManuscriptDynamics of Micro and Nano System

High-performance wafer-scale transfer-free graphene microphones

A repeatable method to fabricate multi-layer graphene (ML-gr) membranes of 2r = 85 - 155 μm (t < 10 nm) with a 100% yield on 100 mm wafers is demonstrated. These membranes show higher sensitivity than a commercial MEMS-Mic combined with an area reduction of 10x. The process overcomes one of the main limitations when integrating graphene diaphragms in microphones due to the absence of automatic transfer methods on non-planarized target substrates. This method aims to overcome this limitation by combining a full-dry release of Chemical Vapor Deposition (CVD) graphene by Deep Reactive Ion Etching (DRIE) and vapor HF (VHF).Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic Components, Technology and MaterialsQN/van der Zant LabDynamics of Micro and Nano SystemsQN/Steeneken La

The Durban Dig-Out Port, Project Durban

The Port of Durban is South Africa's premier port and hub of the region, especially for the Johannesburg (Gauteng Province) area. The current port will eventually not be sufficient to handle the capacity demand. The focus is on the development of a new port in the direct surroundings of Durban. A suitable new location is found at the old international airport. The Durban Dig-out Port is designed to cover a yearly container throughput of 10,000,000 TEU, a yearly liquid bulk throughput of 5,000,000 kL and 300,000 vehicles throughput per year. The governing vessel for the design is a 22,000 TEU container vessel with a length of 430 m, a width of 43.4 m and a draft of 16.3 m. The choice for the 22,000 TEU design vessel is reviewed. Based on global developments in ship manufacturing and a brief look at the developments in South Africa's container trade it is concluded that the 22,000 TEU vessel is recommended for the design of the port. In the proposed port layout the entrance channel is aligned such that it gives possibilities to bring the Isipingo estuary and its protected mangroves back to life. New land becomes available for an extension of the mangrove area and a new natural equilibrium between fresh and salt water inflow can be developed. The direction of the entrance channel also results in the central location of the turning circle and therefore the basins are relatively short. This makes manoeuvring for the vessels in the port convenient. A slight bend in the entrance channel is proposed to mitigate the wave action in the port. A straight entrance channel would lead to large downtime and has a direct impact on the port efficiency. The southern swell waves cannot enter the port due to the breakwaters and the eastern wind waves are either absorbed at the inside of the southern breakwater or at the safety beach at the end of the turning circle. The proposed sand bypass system makes sure that the coastal evolution is sustainable. In the proposed layout two configurations for the breakwaters are distinguished in terms of orientation and length. The proposed breakwaters are based on either a relatively high (10 kn) or low (6 kn) maximum vessel entrance speed. From research with a simplified wave model it is concluded that the shorter breakwaters cause downtime for the liquid bulk terminal during storm conditions from the south. During normal conditions it is however found that the liquid bulk terminal can be operational for more than 99% of the time. Next to that, it is found from the design of the breakwaters' cross sections that the breakwater dimensions become significantly larger at greater depths. However both breakwaters are found stable with numerical stability analysis and in combination with the result of the wave model it is concluded that the shorter configuration is preferred. This leads to significantly lower construction costs and the downtime of the liquid bulk terminal is limited.Civil Engineering and Geoscience

Low power wide spectrum optical transmitter using avalanche mode LEDs in SOI CMOS technology

This paper presents a low power monolithically integrated optical transmitter with avalanche mode light emitting diodes in a 140 nm silicon-on-insulator CMOS technology. Avalanche mode LEDs in silicon exhibit wide-spectrum electroluminescence (400 nm < λ < 850 nm), which has a significant overlap with the responsivity of silicon photodiodes. This enables monolithic CMOS integration of optocouplers, for e.g. smart power applications requiring high data rate communication with a large galvanic isolation. To ensure a certain minimum number of photons per data pulse (or per bit), light emitting diode drivers must be robust against process, operating conditions and temperature variations of the light emitting diode. Combined with the avalanche mode light emitting diode’s steep current-voltage curve at relatively high breakdown voltages, this conventionally results in high power consumption and significant heating. The presented transmitter circuit is intrinsically robust against these issues, thereby enabling low power operation.Dynamics of Micro and Nano SystemsQN/Steeneken La

The avalanche-mode superjunction LED

Accepted Author ManuscriptDynamics of Micro and Nano SystemsQN/Steeneken La

Sensitive Transfer-Free Wafer-Scale Graphene Microphones

During the past decades micro-electromechanical microphones have largely taken over the market for portable devices, being produced in volumes of billions yearly. Because performance of current devices is near the physical limits, further miniaturization and improvement of microphones for mobile devices poses a major challenge that requires breakthrough device concepts, geometries, and materials. Graphene is an attractive material for enabling these breakthroughs due to its flexibility, strength, nanometer thinness, and high electrical conductivity. Here, we demonstrate that transfer-free 7 nm thick multilayer graphene (MLGr) membranes with diameters ranging from 85-155 to 300 μm can be used to detect sound and show a mechanical compliance up to 92 nm Pa-1, thus outperforming commercially available MEMS microphones of 950 μm with compliances around 3 nm Pa-1. The feasibility of realizing larger membranes with diameters of 300 μm and even higher compliances is shown, although these have lower yields. We present a process for locally growing graphene on a silicon wafer and realizing suspended membranes of patterned graphene across through-silicon holes by bulk micromachining and sacrificial layer etching, such that no transfer is required. This transfer-free method results in a 100% yield for membranes with diameters up to 155 μm on 132 fabricated drums. The device-To-device variations in the mechanical compliance in the audible range (20-20000 Hz) are significantly smaller than those in transferred membranes. With this work, we demonstrate a transfer-free method for realizing wafer-scale multilayer graphene membranes that is compatible with high-volume manufacturing. Thus, limitations of transfer-based methods for graphene microphone fabrication such as polymer contamination, crack formation, wrinkling, folding, delamination, and low-Tension reproducibility are largely circumvented, setting a significant step on the route toward high-volume production of graphene microphones. Electronic Components, Technology and MaterialsQN/van der Zant LabDynamics of Micro and Nano SystemsQN/Steeneken La

Nonlinear dynamic identification of graphene's elastic modulus via reduced order modeling of atomistic simulations

Despite numerous theoretical investigations on the mechanical properties of graphene, an accurate identification of its material behavior is still unattained. One hypothesis for this uncertainty is that modeling graphene as a static membrane cannot describe the strong coupling between mechanics and thermodynamics of this structure. Therefore, characterization methods built upon static models could not capture these effects. In this paper, we propose a new method for building a reduced order model for the dynamics of thermalized graphene membranes. We apply the proper orthogonal decomposition algorithm on time responses obtained from molecular dynamics simulations. As a result, a set of orthogonal modes is obtained which are then employed to build a reduced order model. The proposed model can describe the motion of the suspended graphene membrane over the whole spatial domain accurately. Moreover, due to its computational efficiency, it is more versatile for exploring the nonlinear dynamics of the system. This model is then employed for studying the nonlinear dynamics of graphene membranes at large amplitudes to extract Young's modulus. The obtained Young's modulus incorporates the effects of nano-scaled thermally induced dynamic ripples and hence, is temperature and size dependent. Our proposed atomistic modal order reduction method provides a framework for studying the dynamics and extracting the mechanical properties of other nano-structures at the molecular level.Accepted Author ManuscriptDynamics of Micro and Nano SystemsTeam Sander WahlsQN/Steeneken La

Direct Wafer-Scale CVD Graphene Growth under Platinum Thin-Films

Since the transfer process of graphene from a dedicated growth substrate to another substrate is prone to induce defects and contamination and can increase costs, there is a large interest in methods for growing graphene directly on silicon wafers. Here, we demonstrate the direct CVD growth of graphene on a SiO2 layer on a silicon wafer by employing a Pt thin film as catalyst. We pattern the platinum film, after which a CVD graphene layer is grown at the interface between the SiO2 and the Pt. After removing the Pt, Raman spectroscopy demonstrates the local growth of monolayer graphene on SiO2. By tuning the CVD process, we were able to fully cover 4-inch oxidized silicon wafers with transfer-free monolayer graphene, a result that is not easily obtained using other methods. By adding Ta structures, local graphene growth on SiO2 is selectively blocked, allowing the controlled graphene growth on areas selected by mask designDynamics of Micro and Nano SystemsPhotovoltaic Materials and DevicesElectronic Components, Technology and MaterialsEKL Equipmen

Suspended graphene beams with tunable gap for squeeze-film pressure sensing

We present suspended graphene pressure sensors fabricated using an innovative surface micro-machining process. The great advantage of this process is that the molybdenum (Mo) catalyst layer for multi-layer graphene chemical vapor deposition (CVD) is also used as a sacrificial layer to suspend the graphene. This method allows for accurate control of the gap size under the beam by simply varying the catalyst thickness. Furthermore, the need for transfer of the graphene layer is eliminated. Using this method, wafer-scale graphene squeeze-film pressure sensors are fabricated and characterized.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic Components, Technology and MaterialsQN/Steeneken LabQN/van der Zant LabDynamics of Micro and Nano System