Spin polarization and dynamics of DMS colloidal quantum dots
Başlık çevirisi mevcut değil.
- Tez No: 400793
- Danışmanlar: DR. HAO ZENG
- Tez Türü: Doktora
- Konular: Fizik ve Fizik Mühendisliği, Physics and Physics Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 2011
- Dil: İngilizce
- Üniversite: State Unıversıty Of New York At Buffalo
- Enstitü: Yurtdışı Enstitü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: Belirtilmemiş.
Özet
Özet yok.
Özet (Çeviri)
CdSe colloidal quantum dots (QD) is probably one of the most studied QDs due to their tunable bandgap around visible range by quantum confinement. This thesis is composed of three parts that are all based on the investigation of interactions between the carriers and Mn2+ ions incorporated into colloidal CdSe QDs. In the first part, we studied photoluminescence (PL) of Mn2+ doped CdSe QDs at different sizes. We demonstrated excitonic energy of the QDs can be adjusted to lie below or above the Mn2+ characteristic emission by adjusting the size of the QDs and hence quantum confinement. In each case, we investigated PL of Mn2+ doped QDs. We demonstrated that for highly confined QDs PL is dominated by Mn2+ internal transition emission and PL lifetime of excitonic emission is greatly reduced by rapid energy transfer from the conduction band to Mn2+ excited states. In contrast, for bigger QDs, we showed that PL is dominated by excitonic emission and PL lifetime of the excitonic state is three orders of magnitude longer than the PL lifetime of smaller QDs. In the second part, we investigated dynamics of formation of magnetic polarons and carrier spin polarization in Mn2+ doped CdSe QDs using continuous wave magneto-PL and time resolved magneto-PL spectrospies. In Mn2+ doped CdSe QDs, we observed large Zeeman splitting and Landau g factor of two orders of magnitude larger than the g factor for CdSe. Formation of magnetic polarons and carrier spin polarization were measured simultaneously ix through time resolved magneto-PL spectrospy. The observed characteristic time scale of magnetic polaron formation of ~700 ps is surprisingly one order of magnitude longer than the carrier spin relaxation time of ~ 60ps. We attribute this difference to the relatively slow alignment of the correlated Mn2+ ion spins within the exchange field of the carriers. In addition, the increase in the degree of Mn2+ spin alignment during magnetic polaron formation leads to an increase in the carrier spin polarization. In the last part, we investigated the exchange interactions in the CdSe-CdMnSe, core-shell QDs and demonstrated sign reversal of carrier spin polarization through magneto-PL spectroscopy. The sign reversal in the carrier spin polarization is explained by sign reversal of exchange interactions between conduction band electrons and Mn2+ ions due to quantum confinement, together with a different degree of spatial overlap between the electrons and holes and Mn2+ ions in the CdSe-CdMnSe QDs through band engineering.
Benzer Tezler
- Preparation and characterization of nanomagnets showing spin-transfer torque effects
Spin transfer tork etkisi sergileyen nanomagnetlerin hazırlanması ve karakterizasyonlarının belirlenmesi
ŞABAN TIRPANCI
- Computational modeling of overhauser dynamic nuclear polarization in liquids
Sıvılarda overhauser dinamik nükleer polarizasyonunun hesaplamalı modellemesi
SAMİ EMRE KÜÇÜK
- Functionalization of graphene and stoichiometric graphene derivatives
Grafinin fonksiyonelleştirilmesi ve stokiyometrik grafin türevleri
HASAN ŞAHİN
Doktora
İngilizce
2011
İhsan Doğramacı Bilkent ÜniversitesiMalzeme Bilimi ve Nanoteknoloji Ana Bilim Dalı (disiplinlerarası)
Yükleniyor...
- Hyperfine and electric quadrupolar interaction-driven Loschmidt echo in nanoscale nuclear spin baths
Nano ölçekli spin hamamları için en altyapı ve dörtkutup etkileşimleri altında Loschmidt yankısı
EKREM TAHA GÜLDESTE
- Çekirdek manyetik/kuadrupol rezonans deneyleri için ölçüm problarının ve destek elektronik devrelerinin tasarımı
The desing of measurement probes and support electronic circuits for nuclear magnetic/quadrupole resonance experiments
ÖZER ÖNEREN
