AN OVERVIEW OF NANOELECTRONICS AND NANODEVICES

Nanoelectronics is a nascent area of making electronic devices at the atomic scale to utilize small-scale 'quantum' characteristics of nature. As the name suggests, Nanoelectronics refers to employing nanotechnology in building electronic devices/components; especially transistors. Thus, transistor devices which are so small such that inter-atomic cooperation and quantum mechanical characteristics cannot be ignored are known as Nanoelectronics. This article presents Nanoelectronics and Nanodevices, which are the critical enablers that will not only enable mankind to exploit the ultimate technological capabilities of electronic, mechanical, magnetic, and biological systems but also have the potential to play a part in transforming of the systems thus giving rise to new trends that will revolutionize our life style

AN OVERVIEW OF NANOELECTRONICS AND NANODEVICES

Nanoelectronics is a nascent area of making electronic devices at the atomic scale to utilize small-scale 'quantum' characteristics of nature. As the name suggests, Nanoelectronics refers to employing nanotechnology in building electronic devices/components; especially transistors. Thus, transistor devices which are so small such that inter-atomic cooperation and quantum mechanical characteristics cannot be ignored are known as Nanoelectronics. This article presents Nanoelectronics and Nanodevices, which are the critical enablers that will not only enable mankind to exploit the ultimate technological capabilities of electronic, mechanical, magnetic, and biological systems but also have the potential to play a part in transforming of the systems thus giving rise to new trends that will revolutionize our life style

Modern Applications in Optics and Photonics: From Sensing and Analytics to Communication

Optics and photonics are among the key technologies of the 21st century, and offer potential for novel applications in areas such as sensing and spectroscopy, analytics, monitoring, biomedical imaging/diagnostics, and optical communication technology. The high degree of control over light fields, together with the capabilities of modern processing and integration technology, enables new optical measurement systems with enhanced functionality and sensitivity. They are attractive for a range of applications that were previously inaccessible. This Special Issue aims to provide an overview of some of the most advanced application areas in optics and photonics and indicate the broad potential for the future

Advanced characterisation of novel III-nitride semiconductor based photonics and electronics on polar and non-polar substrates

Advanced characterisation has been carried out on a number of novel III-nitride based photonics and electronics, including micro-LED arrays achieved by a direct epitaxy approach, high performance c-plane HEMTs structure achieved by a novel growth method and non-polar GaN/AlGaN HEMTs. In this work, a systematic study has been conducted to understand the electrical properties of these novel devices, demonstrating their excellent properties. Furthermore, the electrical properties are directly related to epitaxial growth, which provides useful information for further improving device performance, such as 2D growth mode for GaN on a large lattice-mismatched substrate which plays an important in obtaining high breakdown and minimised leakage current for HEMTs. Micro-LEDs are the key elements for a microdisplay system, where electrical properties are extremely important. Potentially, any leakage current can trigger to turn on any neighbouring microLEDs which are supposed to be off. Instead of using conventional fabrication methods which normally enhances leakage current, our team developed a direct epitaxy approach to achieving microLED arrays. In this work, detailed I-V characteristic and capacitance measurements have been conducted on these novel microLED devices, demonstrating leakage currents as low as 14.1 nA per LED and a smooth negative capacitance curve instead of odd positive capacitance performances. Furthermore, a comparison study between our microLEDs and the microLEDs prepared using the conventional method indicates our device shows a large reduction of size-dependent inefficiency while such a behaviour is never observed on the microLEDs fabricated by the conventional methods. Unlike the classic two-step method for GaN growth on large lattice-matched sapphire, our team developed a high-temperature AlN buffer technology, where a 2D growth mode, instead of an initial 2D and then 3D growth mode that typically happens for the growth of conventional GaN growth, takes place through the whole growth process. This method allows us to achieve a breakdown electric field strength of 2.5 MV/cm, a leakage current of as low as 41.7 pA at 20 V and saturation current densities as high as 1.1 A/mm. In this work a systematic study has conducted in order to establish a relationship between the excellent device performance and material properties, where a very low screw dislocation density plays a critical role, while our 2D growth method can provide an excellent opportunity for achieving such a low screw dislocation density. This demonstrates the major advantage over the classic two-step method in the growth of power and RF devices. In our case, we have obtained an unintentional doping as low as 2×10^14 cm-3 and screw dislocation densities of 2.3×10^7 cm-2. Compared with c-plane GaN based HEMTs due to its intrinsic polarisation, non-polar GaN/AlGaN HEMTs on r-plane sapphire yields potential advantages in terms of the fabrication of normal-off devices which are particularly important for practical applications. However, it is a great challenge to achieve high quality non-polar GaN on sapphire. Some initial work has been conducted, where the detailed characterisation indicates an electron mobility of 43 cm2 V-1 s-1 has been initially obtained. Furthermore, instead of using an AlGaN/GaN heterostructure with a modulation doping, we deliberately use a quantum well structure as an electron channel, leading to a mobility of 76 cm2 V-1 s-1. Our simulations as well as measurements also provide a guideline for optimising the general epitaxial structure

Avaliação da usabilidade de produtos e serviços "ambient assisted living" numa abordagem "living lab"

Doutoramento em Ciências e Tecnologias da SaúdeO envelhecimento demográfico constitui um desafio à sustentabilidade das sociedades modernas. A população idosa está sujeita a uma evidente diminuição da capacidade funcional, que pode ser minimizada através da utilização de soluções tecnológicas que diminuam a necessidade de assistência e, consequentemente, favoreçam uma velhice autónoma e independente. O Ambient Assited Living (AAL) refere-se a produtos e serviços tecnológicos inteligentes imbuídos no ambiente físico e que são facilitadores de interações inteligentes e naturais entre a pessoa idosa e o ambiente físico. Sendo os produtos e serviços AAL direcionados para a população idosa torna-se fundamental garantir a sua usabilidade. A Classificação Internacional de Funcionalidade, Incapacidade e Saúde (CIF), da Organização Mundial de Saúde, é um elemento chave que permite uma abordagem multidisciplinar, completa e centrada no indivíduo para a avaliação da funcionalidade humana. Segundo a CIF, os produtos e serviços AAL enquadram-se nos fatores ambientais que condicionam a funcionalidade humana. Este trabalho consistiu no desenvolvimento de uma metodologia adequada à avaliação da usabilidade de produtos e serviços AAL que utiliza a CIF como modelo enquadrador. O desenvolvimento desta metodologia baseou-se numa abordagem Living Lab que promove o envolvimento de todas as partes interessadas ao longo do processo de desenvolvimento. A metodologia de avaliação de usabilidade Living Usability Lab (LUL) é composta por três fases: validação conceptual, teste protótipo e teste piloto. A sua consolidação exigiu o desenvolvimento, adaptação e avaliação de um conjunto de instrumentos. Para a validação conceptual foram adaptados e criados inquéritos preliminares, personas e cenários. Para o teste protótipo e teste piloto realizou-se a tradução e adaptação cultural e linguística do Post-Study System Usability Questionnaire (PSSUQ) e da System Usability Scale (SUS), e desenvolveu-se e validou-se a ICF Based Usability Scale (ICF-US). Nos testes de validação dos instrumentos estiveram envolvidos cerca de 60 utilizadores. A metodologia de avaliação de usabilidade LUL foi utilizada num estudo experimental com cerca de 80 utilizadores, em que se consideraram vários projetos de investigação em estádios de desenvolvimento diferentes, e que permitiu demonstrar a sua validade e robustez. Dentro dos vários métodos e ferramentas desenvolvidas, a ICF-US deve ser realçada. Esta foi construída com base no modelo conceptual da CIF e permite, por um lado, realizar uma avaliação global de usabilidade e, por outro, discriminar facilitadores e barreiras o que é fundamental numa abordagem Living Lab. Introduzir a CIF na avaliação de tecnologia é de extrema relevância, pois permite conciliar a área da funcionalidade humana com o AAL e assim estabelecer uma linguagem comum entre as diferentes partes envolvidas no desenvolvimento de produtos e serviços AAL.The demographic aging is a challenge to the sustainability of modern societies. The elderly population suffers a clear decrease of functional capacity, which can be minimized through the use of technological solutions that reduce the need for assistance and, consequently, favors autonomy and independence. The Ambient Assisted Living (AAL) refers to products and intelligent technological services imbued in the physical environment that are facilitators of smart and natural interactions between the elderly people and the physical environment. As AAL products and services are directed to the elderly population it is vital to ensure their usability. The International Classification of Functioning, Disability and Health (ICF), proposed by the World Health Organization, is a key element that allows a multidisciplinary and comprehensive approach based on the individual to assess human functioning. According to the ICF, AAL products and services are considered environmental factors that affect individual functioning. This work consisted in developing an appropriate methodology to evaluate the usability of AAL products and services using the ICF as a conceptual model. The development of this methodology was based in a Living Lab approach, which advocates the involvement of all stakeholders in the development process. The usability evaluation methodology Living Usability Lab (LUL) consists of three phases: concept validation, prototype test and pilot test. Its consolidation required the development, adaptation and validation of a set of instruments. For the conceptual validation preliminary questionnaires, personas and scenarios were developed and adapted. For the prototype test and pilot test the translation, cultural and linguistic adaptation of the Post-Study System Usability Questionnaire (PSSUQ) and the System Usability Scale (SUS) were performed, and the ICF based Usability Scale (ICF-US) was developed and validated. The instruments validation tests involved around 60 users. The usability evaluation methodology was validated in an experimental study with 80 users that considered several research projects in different stages of development, and allowed to demonstrate its validity and robustness. Within the various methods and tools developed ICF-US should be highlighted. This was based on the conceptual model of the ICF and allows on the one hand, make an overall assessment of usability and on the other, discriminate facilitators and barriers which is fundamental in a Living Lab approach. Using the ICF in the evaluation of technology is extremely important because it reconciles the areas of human functioning and AAL, establishing a common language between the different parties involved in the development of AAL products and services