Keywords: molybdenum disulfides, growth mechanism, chemical vapor deposition, transmission electron microscopy Understanding the microscopic mechanism of chemical vapor deposition (CVD) growth of two-dimensional molybdenum disulfide (2D MoS2) is a fundamental issue towards the function-oriented controlled growth. In this work, we report results on revealing the growth kinetics of 2D MoS2 via capturing the nucleation seed, evolution morphology, edge structure and terminations at the atomic scale during CVD growth using the transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) studies. The direct growth of few-and mono-layer MoS2 onto graphene based TEM grids allow us to perform the subsequent TEM characterization without any solution-based transfer. Two forms of seeding centers are observed during 2 characterizations: (i) Mo-oxysulfide (MoOxS2-y) nanoparticles either in multi-shelled fullerene-like structures or in compact nanocrystals for the growth of fewer-layer MoS2;(ii) Mo-S atomic clusters in case of monolayer MoS2. In particular, for the monolayer case, at the early stage growth, the morphology appears in irregular polygon shape comprised with two primary edge terminations: S-Mo Klein edge and Mo zigzag edge, approximately in equal numbers, while as the growth proceeds, the morphology further evolves into near-triangle shape in which Mo zigzag edge predominates. Results from density-functional theory calculations are also consistent with the inferred growth kinetics, and thus supportive to the growth mechanism we proposed. In general, the growth mechanisms found here should also be applicable in other 2D materials, such as MoSe2, WS2 and WSe2 etc.

Monolayer MoS 2 has a promising optoelectronics property, with a bandgap in the visible range; the material is a potential candidate for solar cell applications. In this work, we grew MoS 2 monolayers using a low-pressure chemical vapor deposition approach. To produce uniform wafer-scale MoS 2 monolayer films, precursors molybdenum dioxide (MoO 2 ) and sulfur (S) are utilized. Atomic force microscopy was used to quantify the thickness of the monolayers, and the result was validated by Raman spectroscopy. Transmission electron microscopy (TEM) was used to confirm the crystalline quality of the monolayers, and photoluminescence spectroscopy was used to evaluate their optical properties. We were able to create a Schottky solar cell with a MoS 2 monolayer up to 1 cm 2 area by transferring monolayer film to n-type silicon. The MoS 2 /n-Si Schottky solar cell demonstrated photovoltaic characteristics with a short circuit current density of 14.8 mA cm −2 and an open-circuit voltage of 0.32 V under 100 mW cm −2 illumination. The fill factor and energy conversion efficiency were 53% and 2.46%, respectively, with the highest external quantum efficiency at 530 nm being 44%.

This paper studies and analyzes the ground-based global solar radiation (GSR) data available in the Dohuk governorate.  The data was collected from the Meteorological Directorate in Duhok for six stations: Kani Masi, Bamarni, Amedi, Mangesh, Akre, and Semel.  The highest monthly average values of GSR in Duhok were in June and July, and the lowest values were in December and January. Among all stations, Amedi has the highest value of the monthly mean of GSR (8.7041 kWh/m2/day) followed by Kani Masi at (8.5265), Mangesh at (8.3249), Bamarni at (8.072), Semel (7.0506) and finally Akre 6.1171(kWh/m2/day), while the lowest values of GSR were in December  2018 mostly, except for Semel was in December 2016.  The annual mean of GSR in (kWh/m2/day) for these stations were 5.0168, 4.8311, 4.817, 4.7546, 4.3155, and 3.6183 for Amedi, Kani Masi, Mangesh, Bamarni, Semel, and Akre respectively. The monthly mean of the daily clearness index of the study area peaks is in the mid months of the year (May, June, July, August, and September). KT values experienced a dramatic decrease in March in all stations except Mangesh showed a slight increase. Among all the stations, Akre saw the lowest values in KT ranging from 0.32997 to 0.50686 with an annual average of 0.42443.

Noise is a type of pollution that has a negative impact on human health and well-being. Because of population growth and urbanization, the magnitude and severity of noise pollutionare increasing. This study examines the level of noise throughout Zakho university-faculty of science buildings. Noise levels were measured using a sound level meter at two campus buildings at five different times (9:00 AM –2:00 PM). A total of 180 students (98 females, 82 males) were questioned to collect data. The noise levels were highest at the ground floor of building one were at (11:00AM-12:00PM) and (12:00-1:00 PM), respectively, changing from 60.6 to 73.7 dB at (11:00 AM-12:00 PM) and 63.3-73.8 dB at (12:00-1:00 PM) (12-1:00 PM). These results could be due to students taking a lunch hour after 12:00PM and visiting a café at this site.  The most prevalent direct impact of noise on students was feeling annoyed, which affected 23% of students, followed by headache (18%) and so on. Noise has psychological effects on students such as anxiety (6%) and sleep problems (4%) which all have a low percentage. Lastly, memory lapse (2%) and fatigue (3%) impact on students had a lower proportion when compared to other impacts. However, there was 22% of students did not affect by noise.