Convolutional neural networks (CNNs) are the gold standard in the machine learning (ML) community. As a result, most of the recent studies have relied on CNNs, which have achieved higher accuracies compared with traditional machine learning approaches. From prior research, we learned that multi-class image classification models can solve leaf disease identification problems, and multi-label image classification models can solve leaf disease quantification problems (severity analysis). Historically, maize leaf disease severity analysis or quantification has always relied on domain knowledge-that is, experts evaluate the images and train the CNN models based on their knowledge. Here, we propose a unique system that achieves the same objective while excluding input from specialists. This avoids bias and does not rely on a "human in the loop model" for disease quantification. The advantages of the proposed system are many. Notably, the conventional system of maize leaf disease quantification is labor intensive, time-consuming and prone to errors since it lacks standardized diagnosis guidelines. In this work, we present an approach to quantify maize leaf disease based on adaptive thresholding. The experimental work of our study is in three parts. First, we train a wide variety of well-known deep learning models for maize leaf disease classification, then we compare the performance of the deep learning models and finally extract the class activation heatmaps from the prediction layers of the CNN models. Second, we develop an adaptive thresholding technique that automatically extracts the regions of interest from the class activation maps without any prior knowledge. Lastly, we use these regions of interest to estimate image leaf disease severity. Experimental results show that transfer learning approaches can classify maize leaf diseases with up to 99% accuracy. With a high quantification accuracy, our proposed adaptive thresholding method for CNN class activation maps can be a valuable contribution to quantifying maize leaf diseases without relying on domain knowledge.

The demand for poultry products continues to increase in the world. The prevailing global climate change calls for improved poultry management systems to maintain optimal environmental conditions for boosting productivity. Increased food security based on sound, equitable and sustainable food production systems that utilize modern automation technologies is essential for all nations to be able to achieve the United Nations Sustainable Development Goals (UNSDGs). This proposed study seeks to help achieve some of the UNSDGs which include ending poverty, having zero hunger, good health and well-being, industry innovation and infrastructure. In this article, the design and implementation of a low-cost IoT-based remote poultry management system for small to medium scale producers is presented. Poultry farmers in developing countries are relying on manual poultry management methods which are labor-intensive. The proposed system which was built around the WiFi-enabled ESP8266 NodeMCU microcontroller is capable of monitoring and regulating temperature, humidity, water level, ammonia gas and the lighting system. Security is facilitated by the PIR sensor. The system minimizes employment costs and saves time. Besides, the system has unique capabilities of light scheduling and automatic switching control. The light schedules are pre-configured, and the user can select the required times of illumination. The illumination times in the evening are guided by the age of the birds. Light scheduling improves egg production and also conserves energy. The proposed light scheduling for the system was possible by executing a "cron job". A "cron job" enables the web server to perform repetitive and specific tasks at specific times. Remote monitoring and ease of accessibility of the system via the internet anywhere in the world using devices like smart phones and laptops is facilitated by our proposed web-based portal www.agrorun.co.zw/. The web page also allows users to turn ON or OFF the actuators like fans, blower fan/extractor fan, water pump and the lights.

Barrier height inhomogeneities on Pd/n-type 4H-SiC Schottky barrier diodes in the 300-800 K temperature range have been investigated. Palladium is known to form silicide above 673 K. Temperature dependent current-voltage (I-V) characteristics were analyzed. Barrier height (BH) and ideality factor (n) were found to be strongly temperature dependent. Barrier height increased, whilst ideality factor decreased with increasing in temperature and the Richardson plot showed some deviation from linearity. This was attributed to barrier inhomogeneities at the metal-semiconductor interface which resulted in a distribution of barrier heights. From the modified Richardson plot, the modified Richardson constant, A** was found to be 155 Acm(-2)K(-2) and 87 Acm(-2)K(-2) in the 300-525 K and the 550-800 K temperature ranges respectively.

We have investigated the current-voltage (I-V) characteristics of nickel (Ni), cobalt (Co), tungsten (W) and palladium (Pd) Schottky contacts on n-type 4H-SiC in the 300–800K temperature range. Results extracted from I-V measurements of Schottky barrier diodes showed that barrier height (ФBo) and ideality factor (n) were strongly dependent on temperature. Schottky barrier heights for contacts of all the metals showed an increase with temperature between 300K and 800K. This was attributed to barrier inhomogeneities at the interface between the metal and the semiconductor, which resulted in a distribution of barrier heights at the interface. Ideality factors of Ni, Co and Pd decreased from 1.6 to 1.0 and for W the ideality factor decreased from 1.1 to 1.0 when the temperature was increased from 300K to 800K respectively. The device parameters were compared to assess advantages and disadvantages of the metals for envisaged applications.

Deep level transient spectroscopy shows that defects created by alpha irradiation of germanium are annealed by low energy plasma ions up to a depth of several thousand lattice units. The plasma ions have energies of 2-8eV and therefore can deliver energies of the order of a few eV to the germanium atoms. The most abundant defect is identified as the E-center, a complex of the dopant antimony and a vacancy with and annealing energy of 1.3eV as determined by our measurements. The inductively coupled plasma has a very low density and a very low flux of ions. This implies that the ion impacts are almost isolated both in time and at the surface of the semiconductor. We conclude that energy of the order of an eV is able to travel a large distance in germanium in a localized way and is delivered to the defects effectively. The most likely candidates are vibrational nonlinear wave packets known as intrinsic localized modes, which exist for a limited range of energies. This property is coherent with the fact that more energetic ions are less efficient at producing the annealing effect.

In this work, the electrical properties of dislocation loops and their role in the generation of leakage currents in p-n or Schottky junctions were investigated both experimentally and through simulations. Deep Level Transient Spectroscopy (DLTS) reveals that the implantation of silicon with 2 × 1015 Ge cm−2 and annealing between 1000 °C and 1100 °C introduced two broad electron levels EC − 0.38 eV and EC − 0.29 eV in n-type samples and a single broad hole trap EV + 0.25 eV in the p-type samples. These trap levels are related to the extended defects (dislocation loops) formed during annealing. Dislocation loops are responsible for the significant increase of leakage currents which are attributed to the same energy levels. The comparison between structural defect parameters and electrical defect concentrations indicates that atoms located on the loop perimeter are the likely sources of the measured DLTS signals. The combined use of defect models and recently developed DLTS simulation allows reducing the number of assumptions and fitting parameters needed for the simulation of leakage currents, therefore improving their predictability. It is found that simulations based on the coupled-defect-levels model reproduce well the measured leakage current values and their field dependence behaviour, indicating that leakage currents can be successfully simulated on the exclusive basis of the experimentally observed energy levels.

In this work we present the analysis of small interstitial clusters (ICs) introduced in p-type Si after ion implantation using deep level transient spectroscopy (DLTS) and photoluminescence. Silicon ions with energy 380 keV and fluence of 1.0 x 10(12) cm(-2) have been implanted into bulk p-type Si and post-implant annealing at temperatures between 500 degrees C and 800 degrees C specifically to create small interstitial cluster (ICs) defects. In the samples annealed at 500 degrees C, DLTS spectra show deep level hole traps at E-V + 0.20 eV, E-V + 0.25 eV, E-V + 0.36 eV, and E-V + 0.50 eV. The hole traps E-V + 0.36 eV and E-V + 0.50 eV have been attributed to the small Si self-interstitial clusters. After increasing the post-implant anneals to 600 degrees C there is a significant decrease in defect concentration and all the defects are annealed-out at 700 degrees C. Photoluminescence (PL) spectroscopy of the samples reveals optical band levels, at 1218 nm (1.019 eV), and 1233 nm (1.007 eV) which have both been attributed to interstitial cluster defects. The interstitial cluster-related optical band levels have been observed in the samples annealed at 500 degrees C which correlate well with DLTS measurements. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

In this work, we focused on the analysis of implantation-induced defects, mainly small interstitial clusters (ICs) and {311} defects introduced in n-type Si after ion implantation using deep level transient spectroscopy (DLTS). Silicon ions (at 160 keV or 190 keV) of fluences ranging from (0.1–8.0) × 1013 cm−2 have been implanted into n-type Si and annealed at temperatures between 500 °C and 800 °C specifically to create small ICs or {311}s rod-like defects. In samples dominated by small ICs, DLTS spectra show prominent deep levels at Ec − 0.24 eV and Ec − 0.54 eV. After increasing the fluence and temperature, i.e., reducing the number of small ICs and forming {311} defects, the peak Ec − 0.54 eV is still dominant while other electron traps Ec − 0.26 eV and Ec − 0.46 eV are introduced. There were no observable deep levels in reference, non-implanted samples. The identity and origin of all these traps are interpreted in conjunction with recently developed predictive defect simulation models.

We report on the studies carried out on hydrogen peroxide treated melt-grown, bulk single crystal ZnO samples. Results show the existence of two shallow donors in the as-received ZnO samples with energy levels (37.8±0.3)meV that has been suggested as Zni related and possibly H-complex related and (54.5±0.9)meV, which has been assigned to an Al-related donor. Annealing studies performed on the hydrogen peroxide treated samples reveal the existence of a conductive channel in the samples in which new energy levels have been observed, Zn vacancies, related to the Group I elements, XZn. The surface donor volume concentration of the conductive channel was calculated from a theory developed by Look (2007) [1]. Results indicate an increase in the surface volume concentration with increasing annealing temperature from 60×1017cm−3 at 200°C to 4.37×1018cm-3 at 800°C.

Inductively coupled Ar plasma etching of n-type (Si doped) Gallium Arsenide (GaAs) introduces several electron traps, Ec – 0.04 eV (labelled E1′), Ec – 0.19 eV, Ec – 0.31 eV, Ec – 0.53 eV, and Ec – 0.61 eV (behaving like the well documented M3 and labelled M3′ in this study), of which the metastable defects Ec – 0.04 eV (E1′), and Ec – 0.07 eV are novel. Furthermore, E1′ and M3′ exhibit strong field enhanced carrier emission. Double-correlation deep level transient spectroscopy was used to investigate the field dependent emission behaviour of these two defects. It is shown that for both traps, the observed enhanced emission is due to phonon assisted tunnelling. The latter observation is contrary to the literature reports suggesting that enhanced carrier emission for M3 occurs via the Poole-Frenkel mechanism.

A special fabrication process involving chemical vapor deposition (CVD) was designed in order to fabricate advanced structures used to successfully investigate both deep level transient spectroscopy (DLTS) and leakage currents related to the defects on the same test structures. Silicon ions of energy 160 keV and doses 1.0 x 10(12) cm(-2), 1.0 x 10(13) cm(-2) and 8.0 x 10(13) cm(-2) have been implanted into n-type Si substrate and annealed at 800 degrees C. The highest dose was specifically used to create rod-like {311} extended defects. DLTS spectra show prominent electron traps at E-C - 0.26 eV, E-C - 0.46 eV and E-C - 0.54 eV. There were no observable deep levels in the un-implanted (reference) samples. The identity and origin of all these traps will be interpreted in conjunction with annealing studies, literature results and recently developed predictive defect simulation models. The junction leakage current is found to slightly increase in the presence of {311} defects, which shows that their presence does not significantly increase junction leakage currents in n-type silicon.

The electronic properties of defects introduced by low energy inductively coupled Ar plasma etching of n-type (Si doped) GaAs were investigated by deep level transient spectroscopy (DLTS) and Laplace DLTS. Several prominent electron traps (Ec—0.046eV, Ec—0.186eV, Ec—0.314eV. Ec—0.528eV and Ec—0.605eV) were detected. The metastable defect Ec—0.046eV having a trap signature similar to E1 is observed for the first time. Ec—0.314eV and Ec—0.605eV are metastable and appear to be similar to the M3 and M4 defects present in dc H-plasma exposed GaAs.

Bulk (1 0 0) n-GaSb surfaces have been treated with a sulphur based solution ((NH4)2S/(NH4)2SO4) to which sulphur has been added, not previously reported for the passivation of GaSb surfaces. Au/n-GaSb Schottky barrier diodes (SBDs) fabricated on the treated material show significant improvement compared to that of the similar SBDs on the as-received material as evidenced by the lower ideality factor (n), higher barrier height (ϕb) and lower contact resistance obtained. Additionally, the reverse leakage current, although not saturating, has been reduced by almost an order of magnitude at −0.2 V. The sample surfaces were studied by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The native oxide, Sb–O, present on the as-received material is effectively removed on treating with ([(NH4)2S/(NH4)2SO4]+S) and (NH4)2S. Analysis of the as-received surface by XPS, prior to and after argon sputtering, suggests that the native oxide layer is ≤8.5 nm.

The variation in electrical characteristics of Au/n-Ge (100) Schottky contacts have been systematically investigated as a function of temperature using current–voltage (I−V) measurements in the temperature range 140–300K. The I–V characteristics of the diodes indicate very strong temperature dependence. While the ideality factor n decreases, the zero-bias Schottky barrier height (SBH) (ΦB) increases with the increasing temperature. The I–V characteristics are analyzed using the thermionic emission (TE) model and the assumption of a Gaussian distribution of the barrier heights due to barrier inhomogeneities at the metal–semiconductor interface. The zero-bias barrier height ΦB vs. 1/2kT plot has been used to show the evidence of a Gaussian distribution of barrier heights and values of ΦB=0.615eV and standard deviation σs0=0.0858eV for the mean barrier height and zero-bias standard deviation have been obtained from this plot, respectively. The Richardson constant and the mean barrier height from the modified Richardson plot were obtained as 1.37Acm−2K−2 and 0.639eV, respectively. This Richardson constant is much smaller than the reported of 50Acm−2K−2. This may be due to greater inhomogeneities at the interface.

Ar plasma etching of n-type (Si doped) GaAs introduces several electron traps (E(c) - 0.04 eV, E(c) - 0.07 eV, E(c) - 0.19 eV, E(c) - 0.31 eV, E(c) - 0.53 eV, and E(c) - 0.61 eV). The trap, E(c) - 0.04 eV, labelled E1' and having a trap signature similar to irradiation induced defect E1, appears to be metastable. E(c) - 0.31 eV and E(c) - 0.61 eV are metastable too and they are similar to the M3/M4 defect configuration present in hydrogen plasma exposed n-GaAs. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3673322]

Bulk antimony (Sb) doped germanium (n-Ge) samples with doping concentrations ranging between 7.0 × 1014 cm−3 and 2.5 × 1015 cm−3 were exposed to a dc-hydrogen or helium plasma. Hydrogen exposure resulted in the introduction of a single prominent defect level at EC −0.31 eV. Exposing similar samples to He plasmas introduced the same electron trap. The trap concentration increased linearly with dopant concentration suggesting that Sb may be a component of this plasma-induced trap. Thermal annealing kinetics studies suggested that this defect anneals out by diffusion.

Defects created by a dc hydrogen plasma have been compared to those observed in n-GaAs exposed to an inductively coupled (ICP) Ar plasma. The reference sample (in the case of H-plasma treated material) contained two prominent native deep level electron traps, possibly M4 and EC−0.56 eV, which were both passivated by hydrogen. Plasma treatment also resulted in the formation of a defect observed at 0.58 eV (M3) below the conduction band. This defect transforms back into what is believed to be M4 when annealed at 350 K for 3 h under reverse bias. These two defects compare well with two similar defects observed in the Ar ICP treated samples also showing metastable behavior. Additionally, the electrical characterization of Schottky barrier diodes on n-GaAs, prior to and after hydrogen passivation shows that, depending on the plasma conditions, the plasma ions significantly damage the surface resulting in poor rectifying contacts. The damage is considerably reversed/repaired upon annealing between the room temperature and 573 K (300 °C).

Iridium (Ir) Schottky barrier diodes were deposited on bulk grown (1 0 0) Sb-doped n-type germanium by using the electron beam deposition system. Electrical characterization of these contacts using current-voltage (I-V) and capacitance-voltage (C-V) measurements was performed under various annealing conditions. The variation of the electrical properties of these Schottky diodes can be attributed to combined effects of interfacial reaction and phase transformation during the annealing process. Thermal stability of the Ir/n-Ge (1 0 0) was observed up to annealing temperature of 500 degrees C. Furthermore, structural characterization of these samples was performed by using a scanning electron microscopy (SEM) at different annealing temperatures. Results have also revealed that the onset temperature for agglomeration in a 20 nm Ir/n-Ge (1 0 0) system occurs between 600 and 700 degrees C. (C) 2011 Elsevier B.V. All rights reserved.