Facility layout planning in a lean manufacturing environment

مقدم أطروحة جامعية

al-Khatib, Jamal Nasir Husayn

الجامعة

الجامعة التكنولوجية

الكلية

-

القسم الأكاديمي

قسم هندسة الإنتاج و المعادن

دولة الجامعة

العراق

الدرجة العلمية

ماجستير

تاريخ الدرجة العلمية

2010

الملخص الإنجليزي

This research is considered as a novel work in the field of nanotechnology studies.

We prepared nanostructures porous silicon (NPS) layer by using electrochemical etching process (EC) of p-type silicon wafers which have resistivity (3.5 Ω.cm) and thickness (508 ± 15 μm) in hydrofluoric acid (HF) of concentration (23.5 %) at varies etching time (10, 20, 30, 40, 50 and 60 min), and current density (20 mA).

Structural optical and electrical properties of (NPS) thin layers before and after different rapid thermal annealing process (RTA) temperatures in (300°C, 450°C, 600°C and 750°C ), and at (15sec) annealing time were studied.

The (RTA) process modifies the morphological, optical, and electrical properties of (NPS) as a function to (RTA) temperature.

The morphological properties of the prepared samples before and after annealing have been carried out by using field emission scanning electron microscopy (FESEM) images.

For as-prepared samples we have found that an increasing in pores diameter and decreasing in column width which separate between adjacent pores by increasing etching time .The porosity was increased with increasing etching time from (49 % to 76 %)at etching time from (30 min to 60 min) respectively.

It has been found that the (RTA) process leads surface reconstruction phenomena in (nPSi) layer, reaching to rebuilding the (nPSi) surface and decreasing the pore size in (nPSi) layer with increasing the silicon nanowires as a function (RTA) temperature.

The pore shape was changed from startup shape to cylindrical shape and from irregular pore boundaries to more regular pore boundaries.

The peak of (PL) spectra show blue shift from 545 nm to 540 nm in emission wavelength of as-prepared sample when the etching time increased from 30 min to 60 min respectively.

The (RTA) process leads to a red shift in the peak of (PL) from 739 nm to 753 nm for 30 min etching time, and from 743 nm to 757 nm for 60 min etching time as the (RTA) temperature increased from 450°C to 750°C.

The (PL) intensity undergo a degradation effects as a function to (RTA) temperature was increased from 545 nm for as-prepared to 753 nm for 750 ˚C (RTA) for 30 min etching time, and from 540 nm to 757 nm for 750 ˚C at 60 min etching time.

The silicon nanowires in the (nPSi) layer have been increased from 2.36 nm for as-prepared to 4.18 nm for 750°C (RTA) for 30 min etching time, and from 2.33 nm to 4.24 nm for 750°C at 60 min etching time.

The X-ray diffraction of as-prepared (nPSi) exhibits two peaks at different angles.

This behavior will tend to disappear when the (RTA) temperature increase to 750°C, and the phase of (nPSi) still in mono crystallize phase.

The electrical properties of (nPSi) show an enhancement with thermal treatment.

The dark current is decreased for (nPSi) prepared at 30 min etching time from 3500 to 500 μA / cm2 and from 320 to 100 μA / cm2 for (nPSi) prepared at etching time 60 min at annealing time 15 sec and 750°C.

The ideality factor and the rectification are increasing for the produced (nPSi), with (RTA) process compared with the as-prepared sample.

This study reveals that the (RTA) process could be used for modifying (nPSi) characteristics for many interesting applications due to its superior features.

التخصصات الرئيسية

الكيمياء

الموضوعات

• الخواص الكهربائية
• الخواص الضوئية

• APA
• MLA
• AMA

لغة النص

الإنجليزية

نوع البيانات

رسائل جامعية

رقم السجل

BIM-306136