F.S. Al-Hazmi

Synthesis and characterisation of tin dioxide nanoparticles and effect of annealing temperature

Nanopowder of SnO2 was successfully synthesised by the chemical co-precipitation technique. The product sample was characterised by transmission electron microscope (TEM), X-ray diffraction (XRD) and UV-visible absorption spectrum. Analysis shows that the nanomaterial is found to be phase-pure and nanocrystalline, with a mean particle size around 50 nm. The maximum absorption is observed at around 320 nm. Effect of different annealing temperature on the particle size and shape are also studied. There is no change in the shape and size of these nanoparticles, while annealing them at temperatures ranging from 300°C-600°C. This suggests that the prepared nanoparticles might be useful as gas sensors at hot environments.

Synthesis and characterisation of amorphous SeTe nanorods prepared by ball milling

The amorphous Se97Te3 nanorods were prepared by mechanical milling. The amorphous Se97Te3 materials were used as a starting material. The milled materials were characterisation by XRD, TEM and optical measurement by JASCO, UV/VIS/NIR spectrophotometer in a wavelength region 300 nm-1000 nm. The experimental result shows that an amorphous stage is also achieved during the milling process. TEM analysis showed that after 50 hours of milling time, multi-walled amorphous nanorods were formed with a diameter of about 90 nm and after 60 hours of milling time amorphous nanowires of about 80 nm diameter was formed. The optical absorption measurement indicates that the absorption mechanism is due to indirect transition. It has been observed that the absorption coefficient increases lineally with the increase in photon energy and the optical band gap increases with the increase of milling time.

I-V-T studies on GaN/AlN double barrier resonant tunnelling diodes

Double barrier resonant tunnelling diodes are the first practical nanoelectronic devices which are being actively pursued for applications in electronic circuits. Temperature dependent current-voltage behaviour of GaN/AlN double barrier resonant tunnelling diodes has been studied between 77K and 420K. The absence of resonant tunnelling peak(s) in these nanoelectronic devices has been explained on the presence of traps/defects in the quantum well which tend to destroy coherent tunnelling. Thermal activation energy of the traps has been estimated. A model has been proposed which accounts for the observed I-V-T behaviour.

AC response of AlN/GaN double-barrier resonant tunnelling diodes

Capacitance-voltage (C-V) measurements of GaN/AlN double barrier resonant tunnelling diodes have been made at 77K and 300K. Capacitance-frequency measurements were also made over frequency range of 50Hz-1MHz with a view to study the behaviour of traps located in the quantum well. The role of 2DEG has also been taken into account to explain the observed C-V response. The behaviour of the 2DEG as a function of bias voltages has been simulated by using a computer program and it predicts correctly the vanishing of capacitance at higher biases.

Growth and Electrical Characterization of TlInTe2 Single Crystal

تم بناء وتصميم جهازعالي الكفاءة لإنماء بلورات TlInTe2 أحادية الطور على طريقة بريد جمان محليا. تمت دراسة الموصلية الكهربائية ومعامل هول لهذه البلورات, في المدى من درجات الحرارة 158-473 كلفن. من خلال دراسة الموصلية تبين أنها من نوع P-type, وأن قيمة معامل هولRH=2.3×109 cm3/C عند درجة حرارة الغرفة, و تركيز ناقلة الشحنة هو 2.81×109 cm-3. كما تم تعيين اتساع طاقة الفجوة ?Eg، وكذلك طاقة التأيين لتكونا 0.72eVو 0.113eV على التوالي. كما أن معامل الانتشار, و طول الانتشار, وزمن الاسترخاء تم تعيينهم في هذه الدراسة مع التأكد من ميكانيكية تشتت الشحنات.High efficiency design for single crystal growth from melt based on Bridgman technique is constructed locally and used for growing TlInTe2 crystals. Measurements of Hall coefficient and DC electrical conductivity covering a temperature range from 158 to 473 K were conducted. The investigated samples have P-Type conductivity with RH of 2.3 × 109 cm3/coul. at room temperature and carrier concentrations as 2.81×109 cm-3. Energy gap ?Eg and ionization energy ?Ea were estimated as 0.72 eV and 0.113 eV, respectively. The diffusion coefficient, diffusion length, as well as relaxation time were evaluated, and the scattering mechanism of charge carrier was checked.