The metal tetraphenyl porphyrin (M-TPP) molecule belongs to a wide class of molecules exploited in nature. It has attracted many research interests because of its characteristics like the planar ring-like structure (tetra pyrrole ring), forming an inner cavity enclosed by four phenyl groups. The inner metal ion in the center of the cavity can influence the physical and chemical properties of the compound. The functional groups and the type of metal ion can have a strong influence over the molecular reactivity. Also, the choice of the substrate can affect the performance of organic based devices. One of the possible ways to preserve the electronic and magnetic properties of the molecules is by minimizing the molecular interaction with the substrate by growing them on an ultra- thin metal oxide or passivated metal substrates. In this thesis we present a systematic investigation of M-TPP (Co-and Ni-TPP) molecular layers grown on Fe(001)-p(1 ×1)O, where a well-ordered atomic layer of oxygen passivates the iron substrate. On this passivated substrate, we observe a certain degree of decoupling with the Co(Ni)-TPP molecular layer. The structural analysis by using low energy electron diffraction (LEED) shows a well-ordered commensurate structure of the molecular layer on the substrate. An electron spectroscopy like X-ray photoemission (XPS) was used to investigate the molecular interaction with the substrate, while UV- photoemission spectroscopy (PES) and inverse photoemission spectroscopy (IPES) techniques were exploited in order to investigate the occupied and unoccupied states of the molecules, respectively. Our results show that the Fe(001)-p(1 × 1)O substrate well preserves the electronic structure of the molecule, i.e. the molecular electronic states. viii Starting from these premises, we focused our analysis on the investigation of magnetic ordering of Co(Ni)-TPP on Fe (001)-p(1 × 1)O. A monolayer of Co-TPP grown on Fe(001)-p(1 × 1)O shows a spin splitting of the electronic states indicative of a magnetic ordering with spin resolved photoemission spectroscopy (SR-PES). For Ni-TPP and Zn- TPP a magnetic response is not observed, consistent with the ground state electronic structure of the respective molecules.The metal tetraphenyl porphyrin (M-TPP) molecule belongs to a wide class of molecules exploited in nature. It has attracted many research interests because of its characteristics like the planar ring-like structure (tetra pyrrole ring), forming an inner cavity enclosed by four phenyl groups. The inner metal ion in the center of the cavity can influence the physical and chemical properties of the compound. The functional groups and the type of metal ion can have a strong influence over the molecular reactivity. Also, the choice of the substrate can affect the performance of organic based devices. One of the possible ways to preserve the electronic and magnetic properties of the molecules is by minimizing the molecular interaction with the substrate by growing them on an ultra- thin metal oxide or passivated metal substrates. In this thesis we present a systematic investigation of M-TPP (Co-and Ni-TPP) molecular layers grown on Fe(001)-p(1 ×1)O, where a well-ordered atomic layer of oxygen passivates the iron substrate. On this passivated substrate, we observe a certain degree of decoupling with the Co(Ni)-TPP molecular layer. The structural analysis by using low energy electron diffraction (LEED) shows a well-ordered commensurate structure of the molecular layer on the substrate. An electron spectroscopy like X-ray photoemission (XPS) was used to investigate the molecular interaction with the substrate, while UV- photoemission spectroscopy (PES) and inverse photoemission spectroscopy (IPES) techniques were exploited in order to investigate the occupied and unoccupied states of the molecules, respectively. Our results show that the Fe(001)-p(1 × 1)O substrate well preserves the electronic structure of the molecule, i.e. the molecular electronic states. Starting from these premises, we focused our analysis on the investigation of magnetic ordering of Co(Ni)-TPP on Fe (001)-p(1 × 1)O. A monolayer of Co-TPP grown on Fe(001)-p(1 × 1)O shows a spin splitting of the electronic states indicative of a magnetic ordering with spin resolved photoemission spectroscopy (SR-PES). For Ni-TPP and Zn- TPP a magnetic response is not observed, consistent with the ground state electronic structure of the respective molecules.
La molecola di metallo tetrafenil porfirina (M-TPP) appartiene a una vasta classe di molecole presenti in natura. Ha attratto molto interesse tra i ricercatori per caratteristiche come la sua struttura ad anello planare (anello tetrapirrolico), che forma una cavità interna racchiusa da quattro gruppi fenilici. Lo ione metallico al centro della cavità può influenzare le proprietà fisiche e chimiche del composto. I gruppi funzionali e il tipo di ione metallico possono avere una forte influenza sulla reattività molecolare. Inoltre, la scelta del substrato può influire sulle prestazioni dei dispositivi a base organica. Uno dei modi possibili per preservare le proprietà elettroniche e magnetiche delle molecole è minimizzare l'interazione delle molecole con il substrato, facendole crescere su un ossido di metallo ultrasottile o su un substrato di metallo passivato. In questa tesi presentiamo un'indagine sistematica di strati molecolari di M-TPP (Co- and Ni-TPP) cresciuti su Fe (001)-p(1 × 1)O, in cui uno strato atomico ben ordinato di ossigeno passiva il substrato di ferro. Su questo substrato passivato, osserviamo un certo grado di disaccoppiamento con lo strato molecolare di Co(Ni)-TPP. L'analisi strutturale, effettuata utilizzando la diffrazione di elettroni a bassa energia (LEED), mostra una struttura commensurata e ben ordinata dello strato molecolare sul substrato. La spettroscopia elettronica di fotoemissione con raggi X (XPS) è stata utilizzata per indagare l'interazione delle molecole con il substrato, mentre le tecniche di spettroscopia di fotoemissione UV (PES) e di spettroscopia di fotoemissione inversa (IPES) sono state sfruttate per studiare gli stati occupati e non occupati delle molecole, rispettivamente. I nostri risultati mostrano che il substrato di Fe(001)-p(1 × 1)O preserva bene la struttura elettronica della molecola, cioè gli stati elettronici molecolari. Partendo da queste premesse, abbiamo concentrato la nostra analisi sull'indagine dell'ordinamento magnetico di Co(Ni) -TPP su Fe(001)-p(1 × 1)O. Un singolo strato di Co-TPP cresciuto su Fe(001)-p(1 × 1)O mostra, con la spettroscopia di fotoemissione spin-risolta (SR-PES), una separazione in energia degli stati elettronici rispetto allo spin dell’elettrone che rivela la presenza di un ordinamento magnetico. Per le Ni-TPP e Zn-TPP non si osserva alcuna risposta magnetica, in modo coerente con la struttura elettronica dello stato fondamentale delle rispettive molecole.
Electronic and magnetic properties of thin and ultra-thin Co(Ni)-TPP molecular films on Fe(001)-p(1x1)O
SANGARASHETTYHALLI JAGADEESH, MADAN
Abstract
The metal tetraphenyl porphyrin (M-TPP) molecule belongs to a wide class of molecules exploited in nature. It has attracted many research interests because of its characteristics like the planar ring-like structure (tetra pyrrole ring), forming an inner cavity enclosed by four phenyl groups. The inner metal ion in the center of the cavity can influence the physical and chemical properties of the compound. The functional groups and the type of metal ion can have a strong influence over the molecular reactivity. Also, the choice of the substrate can affect the performance of organic based devices. One of the possible ways to preserve the electronic and magnetic properties of the molecules is by minimizing the molecular interaction with the substrate by growing them on an ultra- thin metal oxide or passivated metal substrates. In this thesis we present a systematic investigation of M-TPP (Co-and Ni-TPP) molecular layers grown on Fe(001)-p(1 ×1)O, where a well-ordered atomic layer of oxygen passivates the iron substrate. On this passivated substrate, we observe a certain degree of decoupling with the Co(Ni)-TPP molecular layer. The structural analysis by using low energy electron diffraction (LEED) shows a well-ordered commensurate structure of the molecular layer on the substrate. An electron spectroscopy like X-ray photoemission (XPS) was used to investigate the molecular interaction with the substrate, while UV- photoemission spectroscopy (PES) and inverse photoemission spectroscopy (IPES) techniques were exploited in order to investigate the occupied and unoccupied states of the molecules, respectively. Our results show that the Fe(001)-p(1 × 1)O substrate well preserves the electronic structure of the molecule, i.e. the molecular electronic states. viii Starting from these premises, we focused our analysis on the investigation of magnetic ordering of Co(Ni)-TPP on Fe (001)-p(1 × 1)O. A monolayer of Co-TPP grown on Fe(001)-p(1 × 1)O shows a spin splitting of the electronic states indicative of a magnetic ordering with spin resolved photoemission spectroscopy (SR-PES). For Ni-TPP and Zn- TPP a magnetic response is not observed, consistent with the ground state electronic structure of the respective molecules.The metal tetraphenyl porphyrin (M-TPP) molecule belongs to a wide class of molecules exploited in nature. It has attracted many research interests because of its characteristics like the planar ring-like structure (tetra pyrrole ring), forming an inner cavity enclosed by four phenyl groups. The inner metal ion in the center of the cavity can influence the physical and chemical properties of the compound. The functional groups and the type of metal ion can have a strong influence over the molecular reactivity. Also, the choice of the substrate can affect the performance of organic based devices. One of the possible ways to preserve the electronic and magnetic properties of the molecules is by minimizing the molecular interaction with the substrate by growing them on an ultra- thin metal oxide or passivated metal substrates. In this thesis we present a systematic investigation of M-TPP (Co-and Ni-TPP) molecular layers grown on Fe(001)-p(1 ×1)O, where a well-ordered atomic layer of oxygen passivates the iron substrate. On this passivated substrate, we observe a certain degree of decoupling with the Co(Ni)-TPP molecular layer. The structural analysis by using low energy electron diffraction (LEED) shows a well-ordered commensurate structure of the molecular layer on the substrate. An electron spectroscopy like X-ray photoemission (XPS) was used to investigate the molecular interaction with the substrate, while UV- photoemission spectroscopy (PES) and inverse photoemission spectroscopy (IPES) techniques were exploited in order to investigate the occupied and unoccupied states of the molecules, respectively. Our results show that the Fe(001)-p(1 × 1)O substrate well preserves the electronic structure of the molecule, i.e. the molecular electronic states. Starting from these premises, we focused our analysis on the investigation of magnetic ordering of Co(Ni)-TPP on Fe (001)-p(1 × 1)O. A monolayer of Co-TPP grown on Fe(001)-p(1 × 1)O shows a spin splitting of the electronic states indicative of a magnetic ordering with spin resolved photoemission spectroscopy (SR-PES). For Ni-TPP and Zn- TPP a magnetic response is not observed, consistent with the ground state electronic structure of the respective molecules.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/166584