1 / 19

The CdSe Nanocrystalline Growth in solutions

The CdSe Nanocrystalline Growth in solutions. Shima Fardad. Introduction. Compound semiconductor deposition from liquid ) aqueous or non-aqueous solutions ( is becoming increasingly popular because : capability of large-area deposition. It has the advantages of economy.

mansfieldm
Download Presentation

The CdSe Nanocrystalline Growth in solutions

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The CdSe Nanocrystalline Growth in solutions Shima Fardad

  2. Introduction • Compound semiconductor deposition from liquid )aqueous or non-aqueous solutions( is becoming increasingly popular because : • capability of large-area deposition. • It has the advantages of economy. • The II/VI semiconductors has been the focus of attention recently for, • Optoelectronic • Photovoltaic solar cells • Photocatalytics • Photoelectro Chemicals • Laser diodes • ...

  3. CdSe growth in: • Glasses • Organic glasses • Colloidal solutions • Chemical solutions • Solution Gels (Sol-gel)

  4. Chemical Deposition(Fabrication Techniques) : • ELECTROCD • Electro Chemical Deposition • PCD • Photo Chemical Deposition • CBD • Chemical Bath Deposition

  5. CdSe Chemical Deposition • Basic idea • Reaction between slowly released Se anion with a free Cd cation. • Controlling the crystalline size by • Growth time • Light intensity • Heating temperature • Wavelength

  6. Effective factorson size

  7. Restricted to electrically conductive materials The films can be made in any thickness from ~1µm to >100µm Electrodeposition

  8. Photo Chemical Deposition • Controlling Deposition by light. • As discussed above • Changing the intensity • Turning off/on • Chemical reaction catalyzed by hv • Need some species (sulfite ions) can supply solvated electrons. • Sulfite ions will release electrons when photo activated.

  9. CdSe PCD reactions Thickness = 300nm ; Time = 120mins Rate = 150nm/h

  10. Chemical Bath Deposition • Large variety of chalcogenide semiconductors • Purely chemical reaction between dissolved precursors (without any charge transfer) • Large area deposition • Various substrates

  11. CdSe CBD • Cadmium acetate + Sodium selenosulfite • Adding small amount of heteropolyacid improves greatly the photoelectrochemical response • Example : Silicotungstic (STA) ; SiW12O40H4 • Changing bath composition gives different mass

  12. CdSe CBD (contd.) • With STA • Less Noisy • Saturated • Without STA • Noisy • Decreases to ZERO

  13. CdSe Growth in CBD • According to Figures we have two-peak profile. • Proves the process takes place in 2 steps. • Two dimensional growth (Cylindrical) • Three dimensional growth (Hemispheroids ) TEM STM

  14. Change in Color (Bulk to Nanocrystal) • As the CdSe grows on the substrate it’s Color changes from yellow to Dark Red. • An aggregation process of the COLLOIDSform.

  15. CdSe in Sol-Gel Films • Sol-Gel Films are prepared by incorporating • Cadmium acetate into a Glass matrix. • Sol-Gel can stabilize cubic forms of nanocrystalline CdSe against transformation to the hexagonal phase. • Causes separation between nanocrystalls. • viscosity will lower the mobility of nanocrystalls. • Porosity of the Sol-Gel

  16. XRD spectra CdSe CD. Fimls CdSe in TiO2 sol-gel CdSe in ZrO2 sol-gel

  17. An application of Electrodepositionfor CdSe • CdSe Nanowire Arrays(embedded in anodic aluminia membrane, AAM) • Uses in • Electronic • Magnetic • Optical devices • Filling the pores of AAM by Electrodeposition method we have a CdSe nanowire. • 60nm in diameter ; 5um in length • Cd/Se significantly depends on the PH (9)

  18. SEM images (highly ordered CdSe nanowire arrays) • A Cross sectional view • A top view image

  19. Best Wishes

More Related