Study Of Gan Low Dimensional Structures On Silicon Substrates Grown By Thermal Vapor Deposition For Photodiode And Solar Cell Applications

Gallium nitride (GaN) is a greatly promising wide band gap semiconductor with applications in high power electronic and optoelectronic devices. Heterostructure solar cell involving GaN low Dimensional (low D) structures on single crystalline silicon (Si) substrates are the preferable choice as they have excellent internal quantum efficiencies, large open-circuit voltages, and low processing cost. This thesis examines the growth of GaN low D structures on Si substrates using inexpensive thermal vapor deposition (TVD) techniques for solar cell and photodiode (PD) devices. The growth was achieved using two methods. The first method involved the growth of GaN low D structures on n-Si (111) in NH3-free environments by TVD via thermal evaporation of GaN powder under different carrier gases, substrate temperatures and deposition times. The result showed that the morphology and shape of GaN low D structures are highly dependent on each parameter. The X-ray diffraction and Raman spectra of the low D structures indicated that the GaN structure had a hexagonal wurtzite structure. The TVD is optimized by using 1h deposition time and 1000ᵒC temperature to obtain uniform dense low D structures with good crystalline quality and hence enhanced performance of PD and solar cell devices

Impact of opioid-free analgesia on pain severity and patient satisfaction after discharge from surgery: multispecialty, prospective cohort study in 25 countries

Background: Balancing opioid stewardship and the need for adequate analgesia following discharge after surgery is challenging. This study aimed to compare the outcomes for patients discharged with opioid versus opioid-free analgesia after common surgical procedures.Methods: This international, multicentre, prospective cohort study collected data from patients undergoing common acute and elective general surgical, urological, gynaecological, and orthopaedic procedures. The primary outcomes were patient-reported time in severe pain measured on a numerical analogue scale from 0 to 100% and patient-reported satisfaction with pain relief during the first week following discharge. Data were collected by in-hospital chart review and patient telephone interview 1 week after discharge.Results: The study recruited 4273 patients from 144 centres in 25 countries; 1311 patients (30.7%) were prescribed opioid analgesia at discharge. Patients reported being in severe pain for 10 (i.q.r. 1-30)% of the first week after discharge and rated satisfaction with analgesia as 90 (i.q.r. 80-100) of 100. After adjustment for confounders, opioid analgesia on discharge was independently associated with increased pain severity (risk ratio 1.52, 95% c.i. 1.31 to 1.76; P < 0.001) and re-presentation to healthcare providers owing to side-effects of medication (OR 2.38, 95% c.i. 1.36 to 4.17; P = 0.004), but not with satisfaction with analgesia (beta coefficient 0.92, 95% c.i. -1.52 to 3.36; P = 0.468) compared with opioid-free analgesia. Although opioid prescribing varied greatly between high-income and low- and middle-income countries, patient-reported outcomes did not.Conclusion: Opioid analgesia prescription on surgical discharge is associated with a higher risk of re-presentation owing to side-effects of medication and increased patient-reported pain, but not with changes in patient-reported satisfaction. Opioid-free discharge analgesia should be adopted routinely