Joana Catarina Martins Mendes

RESEARCH, TEACHING, or OTHER INTERESTS

Electrical and Electronic Engineering, Surfaces, Coatings and Films

Scopus Publications

Bottom-Up Formation of III-Nitride Nanowires: Past, Present, and Future for Photonic Devices
Jungwook Min, Yue Wang, Tae‐Yong Park, Danhao Wang, Bilal Janjua, Dasom Jeong, Gyun Seo Kim, Haiding Sun, Chao Zhao, Joana Catarina Mendes,et al.
Wiley
AbstractThe realization of semiconductor heterostructures marks a significant advancement beyond silicon technology, driving progress in high‐performance optoelectronics and photonics, including high‐brightness light emitters, optical communication, and quantum technologies. In less than a decade since 1997, nanowires research has expanded into new application‐driven areas, highlighting a significant shift toward more challenging and exploratory research avenues. It is therefore essential to reflect on the past motivations for nanowires development, and explore the new opportunities it can enable. The advancement of heterogeneous integration using dissimilar substrates, materials, and nanowires‐semiconductor/electrolyte operating platforms is ushering in new research frontiers, including the development of perovskite‐embedded solar cells, photoelectrochemical (PEC) analog and digital photonic systems, such as PEC‐based photodetectors and logic circuits, as well as quantum elements, such as single‐photon emitters and detectors. This review offers rejuvenating perspectives on the progress of these group‐III nitride nanowires, aiming to highlight the continuity of research toward high impact, use‐inspired research directions in photonics and optoelectronics.


Photochemical modification of a diamond surface using a pulsed UV laser as the energy source
Mariana Silva, Nádia E. Santos, Mariana Pinto, Samuel Guieu, Ricardo Oliveira, Flávio Figueira, Filipe A. Almeida Paz, Miguel Neto, Luis Rino, Jonas Deuermeier,et al.
Elsevier BV



Recent progress in homoepitaxial single-crystal diamond growth via MPCVD
Ying Ren, Xiaogang Li, Wei Lv, Haoyong Dong, Qiaohuan Cheng, Feng Yue, Nicolas Wöhrl, Joana Catarina Mendes, Xun Yang, and Zhengxin Li
Springer Science and Business Media LLC



Improving the Thermal Management of Power LED Arrays with Diamond
Shusmitha Kyatam, Antonio A. Marques, Luis N. Alves, Luis Rodrigues, and Joana C. Mendes
IEEE
The continuous increase of power density levels in components such as RF HEMTs or power LEDs and SiPs often leads to elevated hotspot temperatures that bring along reliability issues. Extracting and transferring the heat from the hotspot to the package and heatsink is however becoming increasingly difficult. One possible solution is the integration of materials with high thermal conductivity at package or board levels. Artificial diamond manufactured by chemical vapor deposition can have a thermal conductivity as high as 1800 W/m-K., a value 4.5 times higher than Cu. In this work we evaluate the potential of mounting several LEDs on diamond boards. To this end, the thermal profile of a $2\\times 2$ array of Cree XLamp XB-D LEDs mounted on MCPCBs and diamond boards was evaluated using Ansys. The impact of replacing the AIN die-carrier in the LED package with diamond was also evaluated. Due to the low thermal conductivity of the MCPCB dielectric layer, replacing the board with diamond has a larger impact than replacing the AIN die-carrier. The thermal benefit of diamond increases as thermal power density rises, either by increasing current levels or by bringing the LEDs closer to one another - even though replacing the MCPCB with a diamond board may induce thermal cross-talk between individual LEDs. By replacing both die-carrier and MCPCB with diamond, for 700 mA the aging of the LEDs slows down $\\approx$ 79-97% depending on the activation energy of the failure mechanisms. Further benefit can be obtained by using die-attach, solders and thermal interface materials and solders with high thermal conductivity.


Diamond coated fiber optic interferometric sensors: fabrication and application
Shusmitha Kyatam, Ricardo Oliveira, Ana M. Rocha, Debarati Mukherjee, Miguel A. Neto, Filipe J. Oliveira, Muhammad A. Khan, Maria R. P. Correia, and Joana C. Mendes
Optica Publishing Group
Diamond films were deposited by chemical vapor deposition (CVD) on the tip of Fabry-Perot (FPI) and multi-mode (MMI) optical fiber interferometers. Diamond provides a robust interface capable of forming covalent bonds between atoms on its surface and receptor molecules, required for biosensing applications. The films were characterized by optical and scanning electron microscopy (SEM), optical profilometry and Raman spectroscopy. The diamond-coated interferometers were tested with different refractive index solutions. The sensors response was 40 ± 1 dB/RIU and −987 ± 70 pm/ RIU for the FPI and −11 ± 1 dB/RIU for the MMI.


A Simple Method to Extract the Thermal Resistance of GaN HEMTs From De-Trapping Characteristics
Benito González, Luís C. Nunes, Jo ao L. Gomes, Joana C. Mendes, and Jose L. Jimenez
Institute of Electrical and Electronics Engineers (IEEE)
This letter proposes a new method for extracting the thermal resistance of GaN-based HEMTs using pulse recovery data. After the device temperature and trapping state are established from different quiescent power dissipations for several base-plate temperatures, the recovery profile of the drain current is measured. The recovery time is then used as a temperature-sensitive electrical parameter to extract the thermal resistance of the device. The proposed method has been applied to a Schottky-gate HEMT on SiC, for which a thermal resistance of 15.7 °C-mm/W was extracted, a value in good agreement with others reported for similar devices. Comparison with the one obtained from a step response is also done. Finally, the uncertainties of the proposed method related to the pulse width, temperature, percentage of the drain current recovery time, and averaging procedure are discussed.


Modeling temperature dynamic effects for high-power light-emitting diodes
Shusmitha Kyatam, Luis Rodrigues, Luis N. Alves, Stanislav I. Maslovski, and Joana C. Mendes
Wiley
SummaryTemperature is a dynamic variable in most electronic devices. As the device operates, it generates heat, which translates in a temperature increase. Available models commonly disregard these variations due to the fact that they manifest at very large time scales. However, temperature dynamic effects have profound implications on the device model and on our common understanding. This paper discusses implications of considering the temperature variations on the current–voltage characteristic curves of power light‐emitting diodes. The main theoretical results establish that the current equation has a memristive nature when temperature is assumed as a dynamical state variable. This hypothesis is then validated experimentally.


The Gemstone Cyborg: How Diamond Films Are Creating New Platforms for Cell Regeneration and Biointerfacing
Nádia E. Santos, Joana C. Mendes, and Susana Santos Braga
MDPI AG
Diamond is a promising material for the biomedical field, mainly due to its set of characteristics such as biocompatibility, strength, and electrical conductivity. Diamond can be synthesised in the laboratory by different methods, is available in the form of plates or films deposited on foreign substrates, and its morphology varies from microcrystalline diamond to ultrananocrystalline diamond. In this review, we summarise some of the most relevant studies regarding the adhesion of cells onto diamond surfaces, the consequent cell growth, and, in some very interesting cases, the differentiation of cells into neurons and oligodendrocytes. We discuss how different morphologies can affect cell adhesion and how surface termination can influence the surface hydrophilicity and consequent attachment of adherent proteins. At the end of the review, we present a brief perspective on how the results from cell adhesion and biocompatibility can make way for the use of diamond as biointerface.


SPI 2023 Held in Aveiro, Portugal
Joana Catarina Mendes and Stefano Grivet-Talocia
Institute of Electrical and Electronics Engineers (IEEE)



Front Matter
IEEE



Improving the reliability of power LEDs with diamond boards
Joana C. Mendes, Luis A. Rodrigues, Sushmitha Kyatam, Luis N. Alves, and Luiz Pereira
IEEE
High power light emitting diodes (LEDs) are much more efficient than conventional light sources like filament bulbs. Nevertheless, heat is still generated, and this directly affects the reliability of these solid-state light (SSL) devices. In order to decrease the operating temperature, these LEDs can be assembled on metal core printed circuit boards (MCPCBs). However, in applications where stability/lifetime is a critical parameter, such as space applications, diamond plates may be considered. These plates are available from manufacturers with metallized tracks for direct assemblage of surface mount devices (SMD). In order to evaluate the impact of the board on SSL reliability, high power Cree LEDs were assembled on MCPCB and diamond plates. The case temperature was measured for different current ratings and the life-time increase induced by the diamond plate was estimated based on the calculation of the acceleration factor (AF). Diamond plates were shown to have a big impact on the life-time; for nominal current level, and depending on the activetion energy of the aging processes, the LED assembled on the MCPCB will age 2.5-8.8 times faster than the one assembled on the diamond plate. For high current ratings the spectrum radiated by the LED assembled on the diamond plate was also shown to be more stable than the one on the MCPCB.


Improving the reliability of power LEDs with diamond boards
Shusmitha Kyatam, Luis Rodrigues, Stanislav Maslovski, Luis N. Alves, and Joana C. Mendes
Elsevier BV



Diamonds for Life: Developments in Sensors for Biomolecules
Nádia E. Santos, Flávio Figueira, Miguel Neto, Filipe A. Almeida Paz, Susana Santos Braga, and Joana C. Mendes
MDPI AG
Diamond-based electrodes and biosensors are interesting in analytics because of their particular set of properties, namely: large potential window, chemical inertness, low baseline current, stability, and transparency. Diamond-based electrodes and biosensors were shown to detect biological molecules such as neurotransmitters and proteins, respectively. In this review, we summarise the different types of diamond electrodes and biosensors based on their type of detection (electrochemical or optical), functionalisation, and target analyte. The last section presents a discussion on the different analytical responses obtained with electrodes or biosensors, according to the type of analyte. Electrodes work quite well for detecting small molecules with redox properties, whereas biosensors are more suited for detecting molecules with a high molecular weight, such as DNA and proteins.


Managing Heat with Diamond: The Example of Diamond/GaN HEMTs
Joana Catarina Mendes and Michael Liehr
IEEE
Diamond is the ultimate thermal management material. Its high breakdown electric field and thermal conductivity, together with the availability of artificial diamond plates and the possibility of growing this material on non-diamond substrates have fueled research in applications where thermal management is of utmost importance. This is the case of gallium nitride (GaN) high electron mobility transistors (HEMTs). Power amplifiers based on GaN-ondiamond wafers are already commercially available, attesting the potential and feasibility of integrating diamond and power components. This work describes the different approaches that can be used to integrate diamond and GaN in hybrid devices with increased power capability.


Diamond/GaN HEMTs: Where from and Where To?
Joana C. Mendes, Michael Liehr, and Changhui Li
MDPI AG
Gallium nitride is a wide bandgap semiconductor material with high electric field strength and electron mobility that translate in a tremendous potential for radio-frequency communications and renewable energy generation, amongst other areas. However, due to the particular architecture of GaN high electron mobility transistors, the relatively low thermal conductivity of the material induces the appearance of localized hotspots that degrade the devices performance and compromise their long term reliability. On the search of effective thermal management solutions, the integration of GaN and synthetic diamond with high thermal conductivity and electric breakdown strength shows a tremendous potential. A significant effort has been made in the past few years by both academic and industrial players in the search of a technological process that allows the integration of both materials and the fabrication of high performance and high reliability hybrid devices. Different approaches have been proposed, such as the development of diamond/GaN wafers for further device fabrication or the capping of passivated GaN devices with diamond films. This paper describes in detail the potential and technical challenges of each approach and presents and discusses their advantages and disadvantages.


Impact of Die Carrier on Reliability of Power LEDs
Shusmitha Kyatam, Luis N. Alves, Stanislav Maslovski, and Joana C. Mendes
Institute of Electrical and Electronics Engineers (IEEE)
High power light emitting diodes (LEDs) suffer from heating effects that have a detrimental impact on the devices characteristics. The use of LED carriers with high thermal conductivity promotes extraction of heat away from the LED junction. Different materials can be used for this purpose, such as alumina, aluminium nitride, and silicon. Diamond has also been gaining momentum for demanding heat management applications. In order to evaluate the impact of the carrier material on the reliability of the devices, the junction temperature of Cree white XLamp XB-D LEDs was obtained with Ansys for various carriers and different LED current levels. The impact of the junction temperature on the LED’s lifetime, emission intensity, footprint, and wavelength stability was then evaluated for each carrier based on the datasheet of the devices. The results provide additional knowledge regarding the impact of the carrier on the performance of the LED.


Modeling dynamic processes of mondego estuary and Óbidos lagoon using delft3D
Joana Mendes, Rui Ruela, Ana Picado, João Pedro Pinheiro, Américo Soares Ribeiro, Humberto Pereira, and João Miguel Dias
MDPI AG
Estuarine systems currently face increasing pressure due to population growth, rapid economic development, and the effect of climate change, which threatens the deterioration of their water quality. This study uses an open-source model of high transferability (Delft3D), to investigate the physics and water quality dynamics, spatial variability, and interrelation of two estuarine systems of the Portuguese west coast: Mondego Estuary and Óbidos Lagoon. In this context, the Delft3D was successfully implemented and validated for both systems through model-observation comparisons and further explored using realistically forced and process-oriented experiments. Model results show (1) high accuracy to predict the local hydrodynamics and fair accuracy to predict the transport and water quality of both systems; (2) the importance of the local geomorphology and estuary dimensions in the tidal propagation and asymmetry; (3) Mondego Estuary (except for the south arm) has a higher water volume exchange with the adjacent ocean when compared to Óbidos Lagoon, resulting from the highest fluvial discharge that contributes to a better water renewal; (4) the dissolved oxygen (DO) varies with water temperature and salinity differently for both systems. On the one hand, for Mondego Estuary during winter the DO levels mainly fluctuate with salinity. On the other hand, for Óbidos Lagoon, DO distribution is determined by both water temperature and salinity. During summer, the high residence time and water temperature limit the DO levels in both systems. The high transferability and superior stability of Delft3D make this model a foundation for realistic simulation and research of distinct estuarine systems, giving support to their maintenance and restoration.


Atomic layer deposition of high-: κ layers on polycrystalline diamond for MOS devices: A review
Aneeta Jaggernauth, Joana C. Mendes, and Rui F. Silva
Royal Society of Chemistry (RSC)
Working in concert, diamond layers and high-κ films impart opportunities for high performance MOS devices. Optimization hinges on their interfacial quality inciting investigation into diamond surface terminations and ALD parameters to ensure success.


Estimation of maximum temperature and thermal crosstalk between two active elements in a PIC: development of a thermal equivalent circuit
Shusmitha Kyatam, Stanislav I. Maslovski, Hugo Neto, Luis N. Alves, and Joana C. Mendes
Optica Publishing Group
The operating temperature plays a key role in the performance and lifetime of photonic integrated circuits (PICs). Miniaturization and increasing heat dissipation promote thermal crosstalk effects and pose additional challenges to the PIC designer. The European Photonics Industry Consortium recommends thermal modeling during design phase. However, a fully numerical optimization of a particular layout requires an unrealistically large number of simulations. Here, we propose a compromise approach: a set of carefully chosen simulations are performed with a multi-physics software. The obtained results are used to derive a linearized equivalent thermal circuit that can be used to maximize the power levels and to minimize the distance between the chosen components while guaranteeing the absence of a thermal crosstalk. For simplification, this model is derived considering a PIC with only two active components. Other parameters are varied, such as the material of the holder (silicon or diamond) and the layer of epoxy that is used to attach the PIC to the holder. The obtained circuit is used to determine the maximum dissipated power or the minimum distance between the components while keeping some predetermined specifications. The model can be extended to contain more elements or to include transient analysis of the temperature distribution.


Interfacial integrity enhancement of atomic layer deposited alumina on boron doped diamond by surface plasma functionalization
A. Jaggernauth, R.M. Silva, M.A. Neto, F.J. Oliveira, I.K. Bdikin, M.P. Alegre, M. Gutiérrez, D. Araújo, J.C. Mendes, and R.F. Silva
Elsevier BV



Physico-chemical characterization of two portuguese coastal systems: Ria de Alvor and Mira estuary
Ana Picado, Joana Mendes, Rui Ruela, João Pinheiro, and João Miguel Dias
MDPI AG
The present study aims to research the physico-chemical processes in two under-researched coastal systems located on the west and south Portuguese coast—Mira Estuary and Ria de Alvor—through the development and exploitation of dedicated coupled physical and water quality models. Both systems are highly dynamic, supporting a wide range of biological diversity; however, they are characterized by distinct environmental and oceanographic conditions, enhancing the importance of a comparative approach. In this context, the Delft3D modeling suite was implemented and successfully calibrated and validated for both systems, accurately reproducing their hydrodynamic, hydrographic, and chemical features. A broad characterization of Mira Estuary and Ria de Alvor was carried out. Results show that the tidal wave interacts differently with the different geomorphology of each estuary. The tidal wave amplitude decreases as it propagates upstream for both estuaries; however, the magnitude for Ria de Alvor is higher. A flood tidal dominance was found for Mira Estuary, allowing the transport of well-oxygenated water into the estuary, contributing to high residence times in the middle estuary and therefore to poor dissolved oxygen (DO) replenishment. Ria de Alvor shifts from ebb dominance at the central area to flood dominance upstream with low residence times, allowing an effective exchange of water properties. Results also reveal that the water temperature is the dominant driver of seasonal dissolved oxygen variations in both estuaries, with the lowest levels occurring during the late summer months when the water temperature is highest. In addition, pH is influenced by biological activity and freshwater inflow.


Deposition of diamond films on single crystalline silicon carbide substrates
Debarati Mukherjee, Filipe Oliveira, Simone Camargo Trippe, Shlomo Rotter, Miguel Neto, Rui Silva, Awadesh Kumar Mallik, Ken Haenen, Carl-Mikael Zetterling, and Joana Catarina Mendes
Elsevier BV



Improvement of an operational forecasting system for extreme tidal events in santos estuary (Brazil)
Joana Mendes, Paulo Leitão, José Chambel Leitão, Sofia Bartolomeu, João Rodrigues, and João Dias
MDPI AG
Forecasting estuarine circulation is a hot topic, especially in densely populated regions, like Santos (Brazil). This paper aims to improve a water-level forecasting system for the Santos estuary, particularly the physical forcing determining the residual tide, which in extreme cases increase the predicting errors. The MOHID hydrodynamic model was implemented with a nested downscaling approach. All automatic procedures to provide a high-resolution real-time forecast system are managed by the AQUASAFE software. Water-level observation and prediction datasets (2016–2017) of five tide gauges in the Santos channel were analyzed, resulting in distinct model configurations, aiming to minimize forecasting inaccuracies. Current MOHID open boundary reference solutions were modified: the astronomical solution was updated from FES2012 to FES2014 whereas the meteorological component (Copernicus Marine Environment Monitoring Service (CMEMS) global solution) time resolution was altered from daily to hourly data. Furthermore, the correlation between significant wave height with positive residual tide events was identified. The model validation presented a minimum Root Mean Square Error (RMSE) of 12.5 cm. Despite FES2014 solution improvements at the bay entrance, errors increase in inner stations were maintained, portraying the need for better bathymetric data. The use of a CMEMS hourly resolution decreased the meteorological tide errors. A linear regression method was developed to correct the residual tide through post-processing, under specific wave height conditions. Overall, the newest implementation increased the water-level forecast accuracy, particularly under extreme events.


CVD diamond films for thermal management applications
Shusmitha Kyatam, Joana C. Mendes, Debarati Mukherjee, Armindo Silva, Luis Alves, Shlomo Rotter, Miguel Neto, Filipe Oliveira, Rui Silva, and Hugo Neto
IEEE
One of the stringent issues in modern electronic applications is related with the necessity of keeping the operating temperature of electronic components within safe levels. The use of passivation, board, and encapsulation materials with large thermal conductivity provides an efficient way of removing the excess heat without increasing the volume and weight of the electronic circuitry. Following this trend, diamond films deposited by chemical vapor deposition (CVD) offer a simple and efficient solution to maintain the operating temperature within safe limits. This paper discusses the use of CVD diamond films with HEMT devices, photonic integrated circuits and high power LEDs.


Thermal management of photonic integrated circuits: Impact of holder material and epoxies
Shusmitha Kyatam, Debarati Mukherjee, Hugo Neto, and Joana C. Mendes
Optica Publishing Group
The thermal management of photonic integrated circuits (PICs) poses a few challenges at the packaging level. The integration of a PIC with a proper holder provides mechanical support and electrical interconnection, as well as spreading of the heat generated during PIC operation. This study proposes and evaluates the thermal behavior of silicon and diamond holders and estimates the impact of integrating them with PICs as a packaged system; to this end, the thermal profile of a PIC with distributed feedback lasers mounted on silicon or diamond holders was simulated for different power levels using ANSYS Mechanical software. The impact of the epoxy resin used to mount the PIC on the holder and the thermal crosstalk between the active components were also evaluated. Based on steady-state thermal analysis, when the PIC is assembled via wire bonding, the replacement of the silicon holder with a diamond holder brings only a marginal advantage. The choice of epoxy has a larger impact on the maximum PIC temperature and the thermal crosstalk between active components. Choosing a large-thermal-conductivity-value epoxy is thus a mandatory requirement in order to guarantee the proper thermal management of PICs and their corresponding holders.