SOĞURMA SPEKTROSKOPİSİ ve GEÇİRİMLİ ELEKTRON MİKROSKOPİ ile KADMİYUM SELENÜR KUANTUM NOKTALARININ OPTİK TESPİTİ

Kuantum noktaları ufacık yarıiletken nanokristallerdir. Boyutları yaklaşık 2 ile 10 nm arasındadır. Eşsiz elektronik ve optik özellikleri nedeniyle büyük ilgi gördüler. Bu parçacıklar çeşitli yollarla sentezlenebilir. Kuantum noktalarının sentez yöntemleri, yukarıdan aşağıya ve aşağıdan yukarıya olarak sınıflandırılabilir. Yukarıdan aşağıya yaklaşım, yığın malzemenin parçalanma sürecidir. Yukarıdan aşağıyanın aksine, kuantum noktaları aşağıdan yukarıya yönteminde malzemenin atomlarından ve moleküllerinden oluşturulur. Bilyalı öğütme, optik litografi, lazer ablasyon ve ark boşaltma bazı yukarıdan aşağıya yöntemlerdir. Ancak, kimyasal indirgeme, ısısal ayrışma, sol-jel ve ultrasonik sprey piroliz aşağıdan yukarıya yöntemlerdir. Bu çalışmada, bir tür aşağıdan yukarıya metot olan kadmiyum selenür kuantum noktalarının kimyasal sıcak enjeksiyon sentez yöntemi anlatılacaktır. Kadmiyum selenür kuantum noktaları, 259oC'de sıcak çözücü içinde büyütülmüştür. Toluen içinde dağılmış kadmiyum selenür kuantum noktalarının konsantrasyonu, birinci eksiton tepesi gözlemlenerek ayarlanmıştır. Kadmiyum selenür kuantum noktalarının ilk eksitonik absorbans tepesi yaklaşık 2,18 eV'de ölçülmüştür. Bu büyütülmüş kuantum noktalarının geçirimli elektron mikroskop fotoğrafı gösterilmiştir. Kadmiyum selenür kuantum noktalarının ortalama çapının yaklaşık 3,48 nm olduğu bulunmuştur. Kadmiyum selenür kuantum noktalarının örgü saçak aralığı ~0,35 nm olarak ölçülmüştür.

Anahtar Kelimeler:

Kuantum noktaları, Kadmiyum selenür, Optik absorbans, Eksiton, Kuşak aralığı

OPTICAL DETECTION of CADMIUM SELENIDE QUANTUM DOTS via ABSORPTION SPECTROSCOPY and TRANSMISSION ELECTRON MICROSCOPY

Quantum dots are tiny semiconductor nanocrystals. Their dimensions are between about 2 and 10 nm. They have attracted much attention due to their unique electronic and optical properties. These particles can be synthesized in a variety of ways. Synthesis methods of quantum dots can be classified into top-down and bottom-up. Top-down approach is a fragmentation process of bulk material. In contrast to top-down, quantum dots are constructed from atoms and molecules of the material at bottom-up procedure. Ball milling, optical lithography, laser ablation and arc-discharge are some top-down methods. However, chemical reduction, thermal decomposition, sol-gel and ultrasonic spray pyrolysis are bottom-up methods. In this study, chemical hot-injection synthesis method of cadmium selenide quantum dots which is a kind of bottom-up procedure will be explained. Cadmium selenide quantum dots have been grown in hot solvent at 259oC. Concentration of cadmium selenide quantum dots dispersed in toluene has been adjusted by observing their first exciton peak. First excitonic absorbance peak of cadmium selenide quantum dots has been measured at around 2.18 eV. Transmission electron microscope photo of these growth quantum dots has been shown. The average diameter of cadmium selenide quantum dots has been found to be approximately 3.48 nm. Lattice fringe spacing of cadmium selenide quantum dots has been measured as ~0.35 nm.

Keywords:

Quantum dots, Cadmium selenide, Optical absorbance, Exciton, Lattice fringe spacing,

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