How to disable scrolling for A Button inside ion-scroll?

Ionic Framework ionic-v3
1

i need to make a fixed position for a button that inside a list that inside an ion-scroll

<ion-scroll scrollY="true">
  <ion-list no-lines>
     <ion-item>
            <button ion-button full large >Submit </button>
     </ion-item>
  </ion-list>
</ion-scroll>

i need this button Submit Button To be a fixed position
i try to use ion-fab but it scroll with a content
thanks in advance